John Gill Commentary Jeremiah 3:11

"And Jehovah said unto me, Backsliding Israel hath showed herself more righteous than treacherous Judah." — Jeremiah 3:11 (ASV)

And the Lord said to me To the Prophet Jeremiah, as in (Jeremiah 3:6) and at or about the same time: the backsliding Israel has justified herself more than treacherous Judah ; that is, was comparatively more righteous; of the two she appeared the most righteous; though neither of them could vindicate their conduct, or justify themselves before God; see (Luke 18:14) .

Judah was most to blame, because that after Israel committed idolatry, and was carried captive, she took no warning by it, but fell into the same sin; and in Manasseh's time committed greater idolatries, and more wickedness, than ever Israel did; and more than even the Amorites themselves, and other Heathen nations, had done, (2 Kings 21:6–11) and though a reformation was made in Josiah's time, it was only feignedly, it was not cordial and hearty; and therefore she is all along here charged with perfidy and treachery.