Albert Barnes Commentary Jeremiah 13:23

"Can the Ethiopian change his skin, or the leopard his spots? then may ye also do good, that are accustomed to do evil." — Jeremiah 13:23 (ASV)

This verse answers the question: Cannot Judah avert this calamity by repentance? No, because her sins are too inveterate. By 'the Ethiopian' (Hebrew: Cushite) is meant not the Cushite of Arabia but the Cushite of Africa; that is, a Black African.