Ver. 19, just as it explains the reformation (ver. 18). [Hitzig: אַחֵר, “another” heart, like the Sept.] The one heart (Acts 4:32) and the new spirit in the inward part are parallel. The old spirit which ruled them inwardly did not permit the harmony and concord which now ensue. But with the gift of a new spirit, the heart of stone, the unnatural element, is at the same time removed out of the flesh, and the natural element—an heart of flesh—is given. It is therefore no antithesis of Holy Spirit and flesh, as elsewhere,—not the contrast of nature and grace, but “a new spirit” and the opposite of the “one heart” that is to be given, i.e. the old spirit, that confront each other,—nature and the unnatural. The manner of expression is peculiar to Ezekiel. As they take away (הֵסִירוּ) all the detestable things and abominations out of the land, so Jehovah takes away (הֲסרֹתִי) the heart of stone out of their flesh. The “stony heart” stands in relation to the idols; so also the “heart of flesh,” “the new spirit,” the “one heart,” stands in relation to the only true God (1 Kings 18:21; Ps. 86:11; James 1:8, 4:8). Comp. the opposite in ver. 21. [Commonly the heart of flesh is taken as a soft heart, receptive of the impressions of divine grace, and the stony heart as the human heart in its natural condition.] Comp. ch. 36:26; Jer. 31:33, 32:39; Ps. 51:12 . Israel, by her apostate, polytheistic conduct, has fallen entirely out of what was natural to her as a people,—that she should be the people of the one true God, the people of His holy law. This unnatural element of her conduct as a nation is to cease by means of the divine gift and working, and so לְמַעַן in Ver. 20 fits in quite simply as defining the purpose. Comp. besides, ver. 12.
Lange, J. P., Schaff, P., Schröder, W. J., Fairbairn, P., Findlay, W., Crerar, T., & Manson, S. (2008). A commentary on the Holy Scriptures: Ezekiel (pp. 127–128). Bellingham, WA: Logos Bible Software.