The clue is in Zechariah Chapter 13:
8 And it shall come to pass in all the land,” Says the Lord, “That two-thirds in it shall be cut off and die, But one-third shall be left in it:
9 I will bring the one-third through the fire, Will refine them as silver is refined, And test them as gold is tested. They will call on My name, And I will answer them. I will say, ‘This is My people’; And each one will say, ‘The Lord is my God.’ ”
The two-thirds cut off are the apostates,
the goats.
The third left remaining are the sheep of Jesus Christ.
Zechariah's context should be seen relative to BABYLON as the Harlot is named BABYLON in the Revelation.
Why were the Jews sent to BABYLON?
Jeremiah said it was because of the "abominations" of the apostates from among them that they were made "desolate",
as he rebuked their burning incense to the QUEEN OF HEAVEN which had resulted in their captivity to BABYLON..
The apostates among them couldn't abide just having God in Heaven alone.
They needed the female to accompany him,
so they adopted one,
in the style of the heathen.
Ezekiel was shown this figure in Chapter 8,
there called the "image of jealousy".
By having such a QUEEN OF HEAVEN,
the actual "god" they obeyed was Tammuz,
the Babylonian version of Baal Peor,
despite their calling him "Yah".
The apostates among the Jews aren't the only ones to have done this.
The first third cut off to BABYLON were the Jewish apostates.
The second third are the Gentile apostates,
sent to a spiritual BABYLON headed by the False Prophet.
Both cut off parts were sent to BABYLON for the very same "abominations" making them "desolate".
The final third,
among the Jews and the Gentiles making up the Heavenly Zion of Jesus Christ,
have been remaining faithful to the One sitting on the Throne,
before whom is shown the Lamb that was slain,
with the Heavenly Sanhedrin who are the Prophets and the Apostles who laid the Foundation of Christ's Congregation,
against which the gates of hell shall not prevail,
the Dragon failing to make them fall away to the QUEEN OF HEAVEN despite his war against them on earth.