Book of Joel Chapter 3 Vs. 20

 The Glorious Future of Judah

But Judah shall dwell for ever, and Jerusalem from generation to generation. Joel 3:20

But Judah shall... Judah will include all the children of Israel from all the tribes in that day, for all will be there (Eze. 37:1-28; 48:1-29); and Jerusalem will be their eternal city (Eze. 48:30-35). The security and prosperity portrayed in Joel 3:17-18 will never again be interrupted. Judah and Jerusalem will be inhabited forever (cf. Amos 9:15; Zec. 14:11). The converted Jews shall dwell in their own land for ever, to the end of the world and never more be carried captive (Eze. 37:25), shall continue evermore, and never more be disturbed by any enemies. They shall dwell safely and peaceably to the end of time.

This is in reference to Christ’s millennial kingdom on earth, which is yet to be fulfilled.

and Jerusalem from... Shall dwell so in like manner, age after age; that is, the inhabitants of Jerusalem, who shall see and enjoy peace and prosperity, both temporal and spiritual, as Jerusalem signifies.

Zec. 8:8 "And I will bring them, and they shall dwell in the midst of Jerusalem: and they shall be my people, and I will be their God, in truth and in righteousness."

Rev. 21:3 "And I heard a great voice out of heaven saying, Behold, the tabernacle of God [is] with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, [and be] their God."

The security and prosperity portrayed in Joel 3:17-18 will never again be interrupted. Judah and Jerusalem will be inhabited forever (cf. Eze. 37:25; Amos 9:15; Zec. 14:11).