Jamieson, Fausset and Brown on Jeremiah 9:24

24. Nothing but an experimental knowledge of God will save the nation.

understandeth--theoretically; in the intellect.

knoweth--practically: so as to walk in My ways (Jr 22:16; Job 22:21; 1Co 1:31).

loving kindness--God's mercy is put in the first and highest place, because without it we should flee from God in fear and despair.

judgment ... righteousness--loving-kindness towards the godly; judgment towards the ungodly; righteousness the most perfect fairness in all cases [Grotius]. Faithfulness to His promises to preserve the godly, as well as stern execution of judgment on the ungodly, is included in "righteousness."

in the earth--contrary to the dogma of some philosophers, that God does not interfere in terrestrial concerns (Psa 58:11).

in these ... I delight--as well in doing them as in seeing them done by others (Mi 6:8; 7:18).