Yahweh makes an amazing, and well-known, promise to Israel in Ezekiel 11: He promises to return them from exile and to “remove from them their heart of stone and give them a heart of flesh” (Ezek 11:19). Whenever I have read this passage or heard it preached, I’ve usually understood Ezekiel’s contrast to have been based on the physical qualities (softness/hardness; warmth/coldness) of “flesh” versus “stone.”
While their physical qualities are likely in the background, an interpretation more sensitive to Ezekiel’s use of language places the focus upon the contrast between the worship of Yahweh and that of Israel’s detestable idols. Earlier in Ezekiel, the rebellious idol-worshippers are described as having foreheads “like the hardest stone, harder than flint” (Ezek 3:9). They are people whose “adulterous hearts” have turned away from Yahweh, and whose eyes have “lusted after their idols” (Ezek 6:9). The connection between a “forehead as hard as stone” and a “heart of stone” is fairly concrete (excuse the pun...). The connection between Yahweh and "flesh" is less so, but arguable nonetheless. As in many prophetic texts, Yahweh is declared to be superior to idols and pagan gods because he is alive and has command of his senses and achieves mighty deeds for his people. Though there is no direct literary link between Yahweh and the “heart of flesh”, such a link can be suggested since the contrast Yahweh draws between "stone" and "flesh" comes in a passage which discusses where Israel's worship and allegiance should lie.
So then, given Ezekiel's use of "stone" and its contrast with "flesh," Yahweh is communicating that the make-up of Israel's heart will mirror the characteristics of the sort of deity they serve. They have worshiped lifeless idols made of stone, and so they receive a lifeless heart of stone. When their worship returns to Yahweh, he gives them a heart of flesh: a living heart from the living God.
