The Time of Jacob's Trouble as it is known (the Tribulation last 7 years) is about Israel. Israel is the hand on God's prophetic clock. These things must come to pass as it is prophesied that Israel on that last day will stand alone with all her enemies around her.
A prophecy:
The word of the LORD concerning Israel. The LORD, who stretches out the heavens, who lays the foundation of the earth, and who forms the human spirit within a person, declares: “I am going to make Jerusalem a cup that sends all the surrounding peoples reeling. Judah will be besieged as well as Jerusalem. On that day, when all the nations of the earth are gathered against her, I will make Jerusalem an immovable rock for all the nations. All who try to move it will injure themselves." (Zechariah 12:1-3).
Why? So that they turn to their Messiah, the One whom they rejected but now call upon!
Although there have been seiges and wars around Jerusalem before this time, we also know that this particular event is still future. The verse says "on that Day", which is always a reference tot he Day of Judgment.
For I do not want you, brethren, to be uninformed of this mystery, lest you be wise in your own estimation, that a partial hardening has happened to Israel until the fullness of the Gentiles has come in; and thus all Israel will be saved; just as it is written, 'The Deliverer will come from Zion, He will remove ungodliness from Jacob.' Romans 11:25-26).
That verse tells us that Jews in Israel will be accepting Jesus as Messiah during the Tribulation. He will remove the partial hardening so that they will see the truth and be able to call out to Him. At long last, they will ask for Jesus!
And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and supplication. They will look on me, the one they have pierced, and they will mourn for him as one mourns for an only child, and grieve bitterly for him as one grieves for a firstborn son. (Zechariah 12:10).
Though rejected by His own people for 2000 years, on that Day He will pour out grace. Not mete it out, not dribble it out, but POUR it out upon those who refused to know Him but now clamor for His grace.
