As it is written - Genesis 17:5.
I have made thee - The word used here in the Hebrew Genesis 17:5 means literally, to give, to grant; and also, to set, or constitute. This is also the meaning of the Greek word used both by the Septuagint and the apostle. The quotation is taken literally from the Septuagint. The argument of the apostle is founded in part on the fact that the past tense is used - I have made thee - and that God spoke of a thing as already done, which he had promised or purposed to do. The sense is, he had, in his mind or purpose, constituted him the father of many nations; and so certain was the fulfillment of the divine purposes, that he spoke of it as already accomplished.
Of many nations - The apostle evidently understands this promise as referring, not to his natural descendants only, but to the great multitude who should believe as he did.
Before him - In his view, or sight; that is, God regarded him as such a father.
Whom he believed - Whose promise he believed; or in whom he trusted.
Who quickeneth the dead - Who gives life to the dead, Ephesians 2:1, Ephesians 2:5. This expresses the power of God to give life. But why it is used here has been a subject of debate. I regard it as having reference to the strong natural improbability of the fulfillment of the prophecy when it was given, arising from the age of Abraham and Sarah, Romans 4:19. Abraham exercised power in the God who gives life, and who gives it as he pleases. It is one of his prerogatives to give life to the dead (νεκρους nekrous), to raise up those who are in their graves; and a power similar to that, or strongly reminding of that, was manifested in fulfilling the promise to Abraham. The giving of this promise, and its fulfillment, were such as strongly to remind us that God has power to give life to the dead.
And calleth ... - That is, those things which he foretels and promises are so certain, that he may speak of them as already in existence. Thus, in relation to Abraham, God, instead of simply promising that he would make him the father of many nations, speaks of it as already done, “I have made thee,” etc. In his own mind, or purpose, he had so constituted him, and it was so certain that it would take place, that he might speak of it as already done.