John Gill Commentary Jeremiah 22:16

"He judged the cause of the poor and needy; then it was well. Was not this to know me? saith Jehovah." — Jeremiah 22:16 (ASV)

He judged the cause of the poor and needy Who could not defend themselves against the rich and the mighty; he took their cause in hand, and, having heard it, determined it in their favour, and did them justice, as princes and civil magistrates ought to do:

then [it was] well [with him] ; this is repeated, not only to show the certainty of it, but that it might be observed, and his example followed:

[was] not this to know me? says the Lord ; it is not by words only, but by deeds, that men show that they know the Lord; for some in words profess to know him, who in works deny him; when princes do the duty of their office, they thereby declare that they know and own the Lord, by, and under whom, they reign; that they have the fear of him before their eyes; this is a practical knowledge of him, and is well pleasing to him.

The Targum is, "is not this the knowledge with which I am well pleased? says the Lord."