Hosea 6:6

mercy--put for piety in general, of which mercy or charity is a branch. not sacrifice--that is, "rather than sacrifice." So "not" is merely comparative (Exo 16:8; Joe 2:13; Joh 6:27; Ti1 2:14). As God Himself instituted sacrifices, it cannot mean that He desired them not absolutely, but that even in the Old Testament, He valued moral obedience as the only end for which positive ordinances, such as sacrifices, were instituted--as of more importance than a mere external ritual obedience (Sa1 15:22; Psa 50:8-9; Psa 51:16; Isa 1:11-12; Mic 6:6-8; Mat 9:13; Mat 12:7). knowledge of God--experimental and practical, not merely theoretical (Hos 6:3; Jer 22:16; Jo1 2:3-4). "Mercy" refers to the second table of the law, our duty to our fellow man; "the knowledge of God" to the first table, our duty to God, including inward spiritual worship. The second table is put first, not as superior in dignity, for it is secondary, but in the order of our understanding.

— Jamieson-Fausset-Brown Commentary (public domain)