Moab is my washpot; over Edom will I cast out my shoe: Philistia, triumph thou because of me. Moab is my washpot - or washing-tub: expressing the ignominious subjection to which David reduced Moab (2 Samuel 8:2). To wash the feet is the office of a slave (John 13:8).
Over Edom will I cast out my shoe. The person who is about to wash his feet casts his shoe to a slave (Matthew 3:11; Acts 13:25). Translate 'to (not over) Edom' (Hengstenberg). Or else the idea of casting the shoe in contempt upon Edom expresses at once the taking possession victoriously of the Edomite land, and the treading upon the pride of Edom, wherewith he had trodden the Israelite land as an invader. So Psalms 60:12; 2 Samuel 8:14. The casting of the shoe was a symbol of transference of possession (Ruth 4:7; Joshua 10:24). So Muis. I prefer this.
Philistia. Moab Edom, Philistia, are mentioned in geographical order, beginning at the east, thence along the south to the west of the Holy Land.
Triumph thou because of me - raise a shout of joy for me, acknowledging me as your king (Psalms 41:11); in order to avert your destruction by me. In Psalms 108:9, "over Philistia will I triumph." Philistia's rejoicing in the triumph of Israel's king is "with trembling," (Psalms 2:11; Psalms 18:44, margin), Philistia, who had once triumphed over Israel's fall beneath herself, must now reluctantly join in Israel's triumph over herself (2 Samuel 8:1; 2 Samuel 8:14; 1 Chronicles 8:13). At the same time there is the covert implication that Israel's triumph will prove ultimately for Philistia's good; because Israel will at last be a blessing to the Gentile world.