Even though the prophets were preachers of repentance and social reform, it is wrong to think of them as the ancient equivalents of a Martin Luther King, Jr. Their shared dream of a better society was not based on an optimistic reading of human nature. Rather, they saw human beings as fundamentally flawed, with sin engraved on the tablets of their hearts (Jer. 17:1). Just as Ethiopians and leopards could not change the colour of their skins, so human beings could not change their sinful nature (Jer. 13:23). . . .
Jeremiah and Ezekiel shared the conviction that human effort could never suffice to save Israel; its heart was too corrupt. What was needed was a heart transplant, the gift of a new heart which had Yahweh's Torah written all over it (Jer. 31:33; Ezek. 36:26–27). Nothing less than a transformation of human nature was required.—NDBT: 124–125.