Albert Barnes Commentary Jeremiah 3:12

"Go, and proclaim these words toward the north, and say, Return, thou backsliding Israel, saith Jehovah; I will not look in anger upon you; for I am merciful, saith Jehovah, I will not keep [anger] for ever." — Jeremiah 3:12 (ASV)

The north – The ten tribes, settled by Salmanezer in the north of Assyria.

I will not cause my anger to fall upon you – literally, I will not cause my face “to fall upon you”: that is, “I will not receive you with averted looks.” The “and” before this clause should be omitted, just as before the next clause, “I will not keep...”

I will not keep – All God’s promises and threats are conditional upon a person’s conduct.