The important thing to understand is that Israel became God's flock when they were baptized unto Moses in the cloud and in the sea (Ps. 77:20, 78:52, 1 Cor. 10:1-2), the flock was divided in the Old Testament, and God promised to unite the flock once again and rule over them in a righteous Kingdom on the Earth as Israel's Shepherd (Jer. 23:1-8, 31:7-10, Ezek. 34:23-24, 36:37-38, Zech. 9:16). Christ, as the "good shepherd", came preaching the gospel of the Kingdom to the lost sheep of the house of Israel. The ministry of John the Baptist marked the beginning of this new dispensation of the gospel of the kingdom. The "lost sheep of the house of Israel" could become part of the "flock" again by getting baptized unto John's baptism of repentance for the remission of sins. Those who obeyed this gospel of the kingdom became part of the "little flock" that would inherit the Kingdom.
I already referenced Jeremiah 23:1-8, it is important to look at it now
 Woe be unto the pastors that destroy and scatter the sheep of my pasture! saith the LORD.
 Therefore thus saith the LORD God of Israel against the pastors that feed my people; Ye have scattered my flock, and driven them away, and have not visited them: behold, I will visit upon you the evil of your doings, saith the LORD.
 And I will gather the remnant of my flock out of all countries whither I have driven them, and will bring them again to their folds; and they shall be fruitful and increase.
 And I will set up shepherds over them which shall feed them: and they shall fear no more, nor be dismayed, neither shall they be lacking, saith the LORD.
 Behold, the days come, saith the LORD, that I will raise unto David a righteous Branch, and a King shall reign and prosper, and shall execute judgment and justice in the earth.
 In his days Judah shall be saved, and Israel shall dwell safely: and this is his name whereby he shall be called, THE LORD OUR RIGHTEOUSNESS.
 Therefore, behold, the days come, saith the LORD, that they shall no more say, The LORD liveth, which brought up the children of Israel out of the land of Egypt;
 But, The LORD liveth, which brought up and which led the seed of the house of Israel out of the north country, and from all countries whither I had driven them; and they shall dwell in their own land.
The shepherds of Israel are clearly going to be the 12 apostles (Matt. 19:28, Luke 12:31-32) and the phrase "neither shall they be lacking" directly corresponds to the passage in Luke 12:31-32.
 And he said unto his disciples, Therefore I say unto you, Take no thought for your life, what ye shall eat; neither for the body, what ye shall put on.
 The life is more than meat, and the body is more than raiment.
 Consider the ravens: for they neither sow nor reap; which neither have storehouse nor barn; and God feedeth them: how much more are ye better than the fowls?
 And which of you with taking thought can add to his stature one cubit?
 If ye then be not able to do that thing which is least, why take ye thought for the rest?
 Consider the lilies how they grow: they toil not, they spin not; and yet I say unto you, that Solomon in all his glory was not arrayed like one of these.
 If then God so clothe the grass, which is to day in the field, and to morrow is cast into the oven; how much more will he clothe you, O ye of little faith?
 And seek not ye what ye shall eat, or what ye shall drink, neither be ye of doubtful mind.
 For all these things do the nations of the world seek after: and your Father knoweth that ye have need of these things.
 But rather seek ye the kingdom of God; and all these things shall be added unto you.
 Fear not, little flock; for it is your Father's good pleasure to give you the kingdom.
As for what I was saying about the ministry of John the Baptist marking the beginning of the new dispensation of the gospel of the kingdom, we can see this very clearly in Isaiah 40. The "lost sheep of the house of Israel" could become part of the "flock" again by getting baptized unto John's baptism of repentance for the remission of sins. Those who obeyed this gospel of the kingdom became part of the "little flock" that would inherit the Kingdom. [Just as they became God's flock in the OT by the baptism unto Moses in the cloud and in the sea--1 Cor. 10:1-2, Ps. 77:20, 78:52).]
Isaiah 40, the famous prophecy of John the Baptist.
 Comfort ye, comfort ye my people, saith your God.
 Speak ye comfortably to Jerusalem, and cry unto her, that her warfare is accomplished, that her iniquity is pardoned: for she hath received of the LORD's hand double for all her sins.
 The voice of him that crieth in the wilderness, Prepare ye the way of the LORD, make straight in the desert a highway for our God.
 Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain:
 And the glory of the LORD shall be revealed, and all flesh shall see it together: for the mouth of the LORD hath spoken it.
 The voice said, Cry. And he said, What shall I cry? All flesh is grass, and all the goodliness thereof is as the flower of the field:
 The grass withereth, the flower fadeth: because the spirit of the LORD bloweth upon it: surely the people is grass.
 The grass withereth, the flower fadeth: but the word of our God shall stand for ever.
 O Zion, that bringest good tidings, get thee up into the high mountain; O Jerusalem, that bringest good tidings, lift up thy voice with strength; lift it up, be not afraid; say unto the cities of Judah, Behold your God!
 Behold, the Lord GOD will come with strong hand, and his arm shall rule for him: behold, his reward is with him, and his work before him.
 He shall feed his flock like a shepherd: he shall gather the lambs with his arm, and carry them in his bosom, and shall gently lead those that are with young.
John the Baptist and the Lord Jesus Christ began preaching the gospel of the Kingdom and offering it to the lost sheep of the house of Israel. Christ was preached as their Shepherd and He said if they followed Him and joined His flock, then they would be kept in His strong hand.
 And Jesus went about all the cities and villages, teaching in their synagogues, and preaching the gospel of the kingdom, and healing every sickness and every disease among the people.
 But when he saw the multitudes, he was moved with compassion on them, because they fainted, and were scattered abroad, as sheep having no shepherd.
Mark 6:34 And Jesus, when he came out, saw much people, and was moved with compassion toward them, because they were as sheep not having a shepherd: and he began to teach them many things.
 These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not:
 But go rather to the lost sheep of the house of Israel.
 And as ye go, preach, saying, The kingdom of heaven is at hand.
 Then Jesus went thence, and departed into the coasts of Tyre and Sidon.
 And, behold, a woman of Canaan came out of the same coasts, and cried unto him, saying, Have mercy on me, O Lord, thou Son of David; my daughter is grievously vexed with a devil.
 But he answered her not a word. And his disciples came and besought him, saying, Send her away; for she crieth after us.
 But he answered and said, I am not sent but unto the lost sheep of the house of Israel.
 Then came she and worshipped him, saying, Lord, help me.
 But he answered and said, It is not meet to take the children's bread, and to cast it to dogs.
 I am the good shepherd, and know my sheep, and am known of mine.
 As the Father knoweth me, even so know I the Father: and I lay down my life for the sheep.
 And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
 My sheep hear my voice, and I know them, and they follow me:
 And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.
 My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand.
 I and my Father are one.
 Then the Jews took up stones again to stone him.
- ISRAEL BECOMES GOD'S FLOCK: Psalms 77:15, 20 "Thou hast with thine arm redeemed thy people, the sons of Jacob and Joseph. Selah...Thou leddest thy people like a flock by the hand of Moses and Aaron." Psalms 78:51-53 "And smote all the firstborn in Egypt; the chief of their strength in the tabernacles of Ham: But made his own people to go forth like sheep, and guided them in the wilderness like a flock. And he led them on safely, so that they feared not: but the sea overwhelmed their enemies."
- ISRAEL WILL BECOME GOD'S FLOCK AGAIN: Isaiah 40:10-11 "Behold, the Lord GOD will come with strong hand, and his arm shall rule for him: behold, his reward is with him, and his work before him. He shall feed his flock like a shepherd: he shall gather the lambs with his arm, and carry them in his bosom, and shall gently lead those that are with young." John 10:27-30 "My sheep hear my voice, and I know them, and they follow me: And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand. I and my Father are one."
It is also important to note the Lord's continual emphasis on Himself being the shepherd of Israel and His emphasis that they should not follow another (John 10:1-16). He emphasized this because there is another shepherd, one who would come "to steal, and to kill, and to destroy" (John 10:10). The Man of Sin, the "idol shepherd".
 And the LORD said unto me, Cast it unto the potter: a goodly price that I was prised at of them. And I took the thirty pieces of silver, and cast them to the potter in the house of the LORD.
 Then I cut asunder mine other staff, even Bands, that I might break the brotherhood between Judah and Israel.
 And the LORD said unto me, Take unto thee yet the instruments of a foolish shepherd.
 For, lo, I will raise up a shepherd in the land, which shall not visit those that be cut off, neither shall seek the young one, nor heal that that is broken, nor feed that that standeth still: but he shall eat the flesh of the fat, and tear their claws in pieces.
 Woe to the idol shepherd that leaveth the flock! the sword shall be upon his arm, and upon his right eye: his arm shall be clean dried up, and his right eye shall be utterly darkened.
Of course the "idol shepherd" is the Man of Sin, sometimes called the "Antichrist". He "leaveth the flock" when he brakes the covenant he made with Israel in the middle of Daniel's 70th Week (Dan. 9:27).
Here are three more passages that need to be looked at when studying the "little flock'.
Jeremiah 31: (the whole chapter is important to this topic)
 For thus saith the LORD; Sing with gladness for Jacob, and shout among the chief of the nations: publish ye, praise ye, and say, O LORD, save thy people, the remnant of Israel.
 Behold, I will bring them from the north country, and gather them from the coasts of the earth, and with them the blind and the lame, the woman with child and her that travaileth with child together: a great company shall return thither.
 They shall come with weeping, and with supplications will I lead them: I will cause them to walk by the rivers of waters in a straight way, wherein they shall not stumble: for I am a father to Israel, and Ephraim is my firstborn.
 Hear the word of the LORD, O ye nations, and declare it in the isles afar off, and say, He that scattered Israel will gather him, and keep him, as a shepherd doth his flock.
 And the word of the LORD came unto me, saying,
 Son of man, prophesy against the shepherds of Israel, prophesy, and say unto them, Thus saith the Lord GOD unto the shepherds; Woe be to the shepherds of Israel that do feed themselves! should not the shepherds feed the flocks?
 Ye eat the fat, and ye clothe you with the wool, ye kill them that are fed: but ye feed not the flock.
 The diseased have ye not strengthened, neither have ye healed that which was sick, neither have ye bound up that which was broken, neither have ye brought again that which was driven away, neither have ye sought that which was lost; but with force and with cruelty have ye ruled them.
 And they were scattered, because there is no shepherd: and they became meat to all the beasts of the field, when they were scattered.
 My sheep wandered through all the mountains, and upon every high hill: yea, my flock was scattered upon all the face of the earth, and none did search or seek after them.
 Therefore, ye shepherds, hear the word of the LORD;
 As I live, saith the Lord GOD, surely because my flock became a prey, and my flock became meat to every beast of the field, because there was no shepherd, neither did my shepherds search for my flock, but the shepherds fed themselves, and fed not my flock;
 Therefore, O ye shepherds, hear the word of the LORD;
 Thus saith the Lord GOD; Behold, I am against the shepherds; and I will require my flock at their hand, and cause them to cease from feeding the flock; neither shall the shepherds feed themselves any more; for I will deliver my flock from their mouth, that they may not be meat for them.
 For thus saith the Lord GOD; Behold, I, even I, will both search my sheep, and seek them out.
 As a shepherd seeketh out his flock in the day that he is among his sheep that are scattered; so will I seek out my sheep, and will deliver them out of all places where they have been scattered in the cloudy and dark day.
 And I will bring them out from the people, and gather them from the countries, and will bring them to their own land, and feed them upon the mountains of Israel by the rivers, and in all the inhabited places of the country.
 I will feed them in a good pasture, and upon the high mountains of Israel shall their fold be: there shall they lie in a good fold, and in a fat pasture shall they feed upon the mountains of Israel.
 I will feed my flock, and I will cause them to lie down, saith the Lord GOD.
 I will seek that which was lost, and bring again that which was driven away, and will bind up that which was broken, and will strengthen that which was sick: but I will destroy the fat and the strong; I will feed them with judgment.
 And as for you, O my flock, thus saith the Lord GOD; Behold, I judge between cattle and cattle, between the rams and the he goats.
 Seemeth it a small thing unto you to have eaten up the good pasture, but ye must tread down with your feet the residue of your pastures? and to have drunk of the deep waters, but ye must foul the residue with your feet?
 And as for my flock, they eat that which ye have trodden with your feet; and they drink that which ye have fouled with your feet.
 Therefore thus saith the Lord GOD unto them; Behold, I, even I, will judge between the fat cattle and between the lean cattle.
 Because ye have thrust with side and with shoulder, and pushed all the diseased with your horns, till ye have scattered them abroad;
 Therefore will I save my flock, and they shall no more be a prey; and I will judge between cattle and cattle.
 And I will set up one shepherd over them, and he shall feed them, even my servant David; he shall feed them, and he shall be their shepherd.
 And I the LORD will be their God, and my servant David a prince among them; I the LORD have spoken it.
 And I will make with them a covenant of peace, and will cause the evil beasts to cease out of the land: and they shall dwell safely in the wilderness, and sleep in the woods.
 And I will make them and the places round about my hill a blessing; and I will cause the shower to come down in his season; there shall be showers of blessing.
 And the tree of the field shall yield her fruit, and the earth shall yield her increase, and they shall be safe in their land, and shall know that I am the LORD, when I have broken the bands of their yoke, and delivered them out of the hand of those that served themselves of them.
 And they shall no more be a prey to the heathen, neither shall the beast of the land devour them; but they shall dwell safely, and none shall make them afraid.
 And I will raise up for them a plant of renown, and they shall be no more consumed with hunger in the land, neither bear the shame of the heathen any more.
 Thus shall they know that I the LORD their God am with them, and that they, even the house of Israel, are my people, saith the Lord GOD.
 And ye my flock, the flock of my pasture, are men, and I am your God, saith the Lord GOD.
Notice how it repeatedly says that God would seek that which was lost (vs. 16). This corresponds to Luke 19:9-10 "And Jesus said unto him, This day is salvation come to this house, forsomuch as he also is a son of Abraham. For the Son of man is come to seek and to save that which was lost."
It is important to notice that Israel was scattered during the "cloudy and dark day" (verse 12). This is a reference to the Day of the Lord according to Zephaniah 1...
 The great day of the LORD is near, it is near, and hasteth greatly, even the voice of the day of the LORD: the mighty man shall cry there bitterly.
 That day is a day of wrath, a day of trouble and distress, a day of wasteness and desolation, a day of darkness and gloominess, a day of clouds and thick darkness,
 A day of the trumpet and alarm against the fenced cities, and against the high towers.
 And I will bring distress upon men, that they shall walk like blind men, because they have sinned against the LORD: and their blood shall be poured out as dust, and their flesh as the dung.
 Neither their silver nor their gold shall be able to deliver them in the day of the LORD's wrath; but the whole land shall be devoured by the fire of his jealousy: for he shall make even a speedy riddance of all them that dwell in the land.
Also notice verse 15 of Ezekiel 34 where God said "I will cause them to lie down". This is a reference to the "rest" of the Millennium. (Heb. 4:1-11 also mentions this rest.)
 For the LORD will have mercy on Jacob, and will yet choose Israel, and set them in their own land: and the strangers shall be joined with them, and they shall cleave to the house of Jacob.
 And the people shall take them, and bring them to their place: and the house of Israel shall possess them in the land of the LORD for servants and handmaids: and they shall take them captives, whose captives they were; and they shall rule over their oppressors.
 And it shall come to pass in the day that the LORD shall give thee rest from thy sorrow, and from thy fear, and from the hard bondage wherein thou wast made to serve,
 That thou shalt take up this proverb against the king of Babylon, and say, How hath the oppressor ceased! the golden city ceased!
 The LORD hath broken the staff of the wicked, and the sceptre of the rulers.
 He who smote the people in wrath with a continual stroke, he that ruled the nations in anger, is persecuted, and none hindereth.
 The whole earth is at rest, and is quiet: they break forth into singing.
Jeremiah 30:10 Therefore fear thou not, O my servant Jacob, saith the LORD; neither be dismayed, O Israel: for, lo, I will save thee from afar, and thy seed from the land of their captivity; and Jacob shall return, and shall be in rest, and be quiet, and none shall make him afraid.
[context is God saving Israel from the "time of Jacob's trouble".]
Jeremiah 46:27 But fear not thou, O my servant Jacob, and be not dismayed, O Israel: for, behold, I will save thee from afar off, and thy seed from the land of their captivity; and Jacob shall return, and be in rest and at ease, and none shall make him afraid.
One final passage that should be looked at is Ezekiel 36:19-38, but for sake of space here is verses 37-38.
"Thus saith the Lord GOD; I will yet for this be inquired of by the house of Israel, to do it for them; I will increase them with men like a flock. As the holy flock, as the flock of Jerusalem in her solemn feasts; so shall the waste cities be filled with flocks of men: and they shall know that I am the LORD."
Why is all this important?
#1 Because it is in the Bible. (2 Tim. 3:16-17)
#2 It proves that the ministry of John the Baptist and the gospel of the Kingdom preached throughout Matthew through John are not written about the Church the Body of Christ, they are about Israel and the Kingdom that will be established in the Earth. Which is why the doctrine of those books does not always match the Pauline epistles written to the Gentiles under the Dispensation of Grace (Rom. 11:13, 11:25, 15:15-16, 16:25, Eph. 3:2).
#3 All the scriptures we looked at are about Daniel's 70th Week and they show that the rapture that happens at the end of the week is ISRAEL'S and has nothing to do with the Church the Body of Christ, our rapture is BEFORE Daniel's 70th Week (1 Thes. 1:10, 5:4, 5:9, Rom. 5:9, Phil. 3:20-21).
#4 It gives us a better understanding of Christ and what His earthly ministry was about.