"By Myself I have sworn, declares the LORD, because you have done this and have not withheld your son, your only son, I will surely bless you."
The fact that God swears by Himself is something great and wonderful. The author of the Epistle to the Hebrews saw this here and weighed it carefully (6:13). For it is an indication of a heart burning with inexpressible love and with a desire for our salvation, as though God were saying: "I desire so greatly to be believed and long so intensely to have My words trusted that I am not only making a promise but am offering Myself as a pledge. I have nothing greater to give as a pledge, because as surely as I am God, there is nothing greater than I. If I do not keep My promises, I shall no longer be He who I am." . . . Accordingly, let us also bear in mind that God enlarges His promise to such an outstanding extent that it surpasses all thinking and faith; for He strengthens and confirms it by His majesty, in order that we may have no reason whatever to mistrust and doubt. . . . God accommodates Himself completely to our weakness. It should be enough if He moved one finger to bear witness of His fatherly goodwill toward us. But now He offers us His Word, and He not only promises but even takes an oath and invokes evil upon and curses Himself—if one were permitted to speak this way—in order to bless us.