Genesis 22:17

17.Thy seed shall possess the gate of his enemies. He means that the offspring of Abraham should be victorious over their enemies; for in the gates were their bulwarks, and in them they administered judgment. Now, although God often suffered the enemies of the Jews tyrannically to rule over them; yet he so moderated their revenge, that this promise always prevailed in the end. Moreover, we must remember what has before been stated from Paul, concerning the unity of the seed; for we hence infer, that the victory is promised, not to the sons of Abraham promiscuously, but to Christ, and to his members, so far as they adhere together under one Head. For unless we retain some mark which may distinguish between the legitimate and the degenerate sons of Abraham, this promise will indiscriminately comprehend, as well the Ishmaelites and Idumeans, as the people of Israel: but the unity of a people depends on its head. Therefore the prophets, whenever they wish to confirm this promise of God, assume the principle, that they who have hitherto been divided, shall be united, under David, in one body. What further pertains to this subject may be found in the twelfth chapter Genesis 12:1