Jamieson, Fausset and Brown on Ezekiel 36:26

26. new heart--mind and will.

spirit--motive and principle of action.

stony heart--unimpressible in serious things; like the "stony ground" (Mt 13:5, 20), unfit for receiving the good seed so as to bring forth fruit.

heart of flesh--not "carnal" in opposition to "spiritual"; but impressible and docile, fit for receiving the good seed. In Eze 18:31 they are commanded, "Make you a new heart, and a new spirit." Here God says, "A new heart will I give you, and a new spirit will I put within you." Thus the responsibility of man, and the sovereign grace of God, are shown to be coexistent. Man cannot make himself a new heart unless God gives it (Php 2:12, 13).