Albert Barnes Commentary Jeremiah 31:7

"For thus saith Jehovah, Sing with gladness for Jacob, and shout for the chief of the nations: publish ye, praise ye, and say, O Jehovah, save thy people, the remnant of Israel." — Jeremiah 31:7 (ASV)

Among - Or, because of. Israel is the chief, or first, of the nations (Deuteronomy 26:19), and Yahweh summons mankind to rejoice, because the remnant of Israel is about to be restored to its old position.