17 (as it is written, “I have made you a father of many nations”) in the presence of Him whom he believed—God, who gives life to the dead and calls those things which do not exist as though they did;
Father — Genesis 17:5 — Neither shall thy name any more be called Abram, but thy name shall be Abraham; for a father of many nations have I made thee. It says “I have” even though it hadn’t yet occurred because God’s promise made it sure.
gives life to the dead — in this case, Sarah and Abraham’s bodies were dead to child-bearing but God made them alive.