New Defender's Study Bible Notes
13:23 change his skin. God has ordained reproduction only “after his kind” (Genesis 1:25), and neither environment nor heredity can change that. Just so, only a miraculous regeneration can change man’s heart and nature.
13:23 the Ethiopian. “Ethiopian” is “Cushite,” a descendant of Cush, first son of Ham. The reference to the Ethiopian’s “skin” indicates that it was permanently different from that of other descendants of Noah, presumably black. The inference, though never expressed directly in Scripture, is that Cushites who had migrated across the Red Sea from their first home (after Babel) in southern Arabia to colonize Ethiopia later colonized other parts of central and southern Africa as well, so that all tribes of black-skinned Africans originally descended from Cush.