(1.) God will plant good principles in them; he will make the tree good, v. 19. This is a gospel promise, and is made good to all those whom God designs for the heavenly Canaan; for God prepares all for heaven whom he has prepared heaven for. It is promised, [1.] That God will give them one heart, a heart entire for the true God and not divided as it had been among many gods, a heart firmly fixed and resolved for God and not wavering, steady and uniform, and not inconstant with itself. One heart is a sincere and upright heart, its intentions of a piece with its professions. [2.] That he will put a new spirit within them, a temper of mind agreeable to the new circumstances into which God in his providence would bring them. All that are sanctified have a new spirit, quite different from what it was; they act from new principles, walk by new rules, and aim at new ends. A new name, or a new face, will not serve without a new spirit. If any man be in Christ, he is a new creature. [3.] That he will take away the stony heart out of their flesh, out of their corrupt nature. Their hearts shall no longer be, as they have been, dead and dry, and hard and heavy, as a stone, no longer incapable of bearing good fruit, so that the good seed is lost upon it, as it was on the stony ground. [4.] That he will give them a heart of flesh, not dead or proud flesh, but living flesh; he will make their hearts sensible of spiritual pains and spiritual pleasures, will make them tender, and apt to receive impressions. This is God's work, it is his gift, his gift by promise; and a wonderful and happy change it is that is wrought by it, from death to life. This is promised to those whom God would bring back to their own land; for then such a change of the condition is for the better indeed when it is accompanied with such a change of the heart; and such a change must be wrought in all those that shall be brought to the better country, that is, the heavenly.