New Defender's Study Bible Notes
13:5 hid it by Euphrates. Critics have claimed Jeremiah could not have made such a journey. But the upper Euphrates was not more than five hundred miles from Jerusalem, and a journey of this distance was quite possible at that time.
13:16 the dark mountains. Babylon was a “destroying mountain” that God would eventually make a “burnt mountain” (Jeremiah 51:25), and Judah was about to stumble upon it, and enter gross darkness and the shadow of death. God’s people today face the same danger from “MYSTERY, BABYLON THE GREAT” (Revelation 17:5), the pagan evolutionary pantheism originated by Nimrod at Babel, “the mother of abominations of the earth.”
13:16 feet stumble. Christ is the stone of stumbling for the lost, but the foundation stone for the saved. See notes on Isaiah 8:14; Matthew 21:44.
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.