The Bible says there is going to be what is known as the rapture:
For the Lord himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first.
Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air. And thus we shall always be with the Lord. 1 Thess 4:16, 17.
After the rapture will come the tribulation, a time of terrible suffering for those who remain on the earth. The Old Testament calls it the time of Jacob's trouble (Jer 30:6 - 9; Matt 24:15 - 28; Rev 7:13 - 17).
There may be a number of reasons for the tribulation. But one reason certainly is to bring the Jews back to God. How will they come?
In that day a fountain shall be opened for the house of David and for the inhabitants of Jerusalem, for sin and for uncleanness Zech 13:1. What fountain is this?
There is a fountain filled with blood,
Drawn from Immanuel's veins;
And sinners plunged beneath that flood
Lose all their guilty stains.
They will wash as Gentile believers have washed, trusting for forgiveness in the shed blood of the Jewish Messiah. See Zech 12:10 - 14. Then Jesus will return. Jesus cannot come back to earth until the Jews are ready to receive Him. Which seems like a very good reason to pray for the Jewish people. (In speaking of His return, I do not speak of the rapture, which could occur at any time. He does not come to earth at the rapture, but appears in the clouds to take His people home.)
His return is recorded in Rev 19:11 - 16:
Then I saw heaven opened, and behold, a white horse. And he who sat on him was called Faithful and True, and in righteousness he judges and makes war.
His eyes were like a flame of fire, and on is head were many crowns. He had a name written that no man knew except himself.
He was clothed with a robe dipped in blood, and his name is called the Word of God.
And the armies in heaven, clothed in fine linen, white and clean, followed him on white horses.
Now out of his mouth goes a sharp sword, that with it he should strike the nations. And he himself will rule them with a rod of iron. He himself treads the winepress of the fierceness and wrath of Almighty God.
And he has on his robe and on his thigh a name written:
KING OF KINGS
AND LORD OF LORDS.
He will come back in power and great glory. All who have refused His forgiveness will find judgment. Those who went to be with Him at the rapture will return with Him. He will set up His kingdom on the earth.