In many sections of the Old Testament the Jewish prophets predicted in great detail the worldwide regathering of Israel. There many passages that describe the Jews coming back to the land in unbelief (Ezekiel 20:33-38; 22: 17-22; Zephaniah 2: 1-2 etc.) These passages describe the Jews coming back after a major persecution and before a major persecution. The 1st one was the Nazi Holocaust. The next one will be the Great Tribulation. Hitler eliminated 1/3 of the world’s Jews. Antichrist will kill 2/3 of them (Zechariah 13:8).
Jesus did say in His Olivet Discourse that the final regathering would occur finally and completely after His Second Coming. Jesus’ account of this re-gathering is found in Matthew 24:31 and in Mark 13:27.
The Matthew account reads:
Matthew 24:31 And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.
The Mark Passage reads:
Mark 13:27 And then shall he send his angels, and shall gather together his elect from the four winds, from the uttermost part of the earth to the uttermost part of heaven.
Following the Second Coming, Christ will send His angels all over the world to re-gather every Jew and bring them back into their Land. The reference to the Matthew passage is Isaiah 27:12-13, which prophesied that the final restoration of Israel will be signaled by the sound of a great trumpet. The reference to the Mark passage is Deuteronomy 30:4, which also emphasizes that the final restoration will come from the earth as well as heaven. Those who are gathered from the uttermost parts of the earth will be living in Israel, the one-third Remnant that survives the Tribulation. Those who are gathered from the uttermost part of Heaven will be the resurrected Old Testament saints. This part of the Olivet Discourse summarizes many Old Testament prophecies, specifying that the final world-wide restoration will come only after the Second Coming, not before (Isaiah 11:11-12:6; 43:5-7; Jeremiah 23:5-8; 31:7-14; Ezekiel11:16-21; 20:40-42; 36:22-31).