Albert Barnes 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—or, Again, once more. The prophet now turns to Judah. By the mountain of holiness is meant not the temple only, but all Jerusalem, of which the temple was the most sacred spot, and that by which all the rest was made holy.