Charles Ellicott Commentary Jeremiah 31:23

"Thus saith Jehovah of hosts, the God of Israel, Yet again shall they use this speech in the land of Judah and in the cities thereof, when I shall bring again their captivity: Jehovah bless thee, O habitation of righteousness, O mountain of holiness." — Jeremiah 31:23 (ASV)

As yet they shall use this speech in the land of Judah ... —Better, Once more, or yet again. The phrase is the same as in Jeremiah 31:5.

The eye of the prophet turns from the northern kingdom to that of Judah, and sees it also as a sharer in the restoration. Jerusalem should be blessed, and be worthy of blessing—once more a faithful city, a holy mountain, righteousness dwelling in it (Isaiah 1:21). The “holy mountain” is used with a special reference to Moriah and the Temple.