Schin.
21. Rejoice—at our calamities (Ps 137:7). This is a prophecy that Edom should exult over the fall of Jerusalem. At the same time it is implied, Edom's joy shall be short-lived. Ironically she is told, Rejoice while thou mayest (Ec 11:9).
cup—for this image of the confounding effects of God's wrath, see Jer 13:12; 25:15, 16, 21; as to Edom, Jer 49:7-22.