Jeremiah 13:23

The Jerusalemites were so steeped in evil that it was impossible for them to change. They could no more change then than the dark Ethiopian could change the color of his skin or the leopard his spots. They had passed the point of no return; repentance was now impossible for them (cf. Hebrews 6:4-6).

"Here is a classic example of loss of freedom of the will through persistent sinning. Sin becomes natural. Jeremiah is speaking of the force of habit, not denying freedom of choice (cf. John 8:34)." [Note: Feinberg, p. 466.]