“A father of many nations have I made you,” said God to ancient Abraham. We don’t know his mental or physical health, but we do know this much — the old patriarch, now about 100 years of age, cannot begat a child. Even if he could, his wife Sarah, past 90 herself, cannot contribute to the process.
But there is a third character in this scenario, and that makes all the difference. It is God. Not just any god. Not even a fertility god, such as the Canaanite baals. This is Jehovah God, the Creator of heaven and earth. The God who “gives life to the dead and calls into being that which does not exist” (Rom. 4:17).
When this God promises something — even something so patently outlandish as Abraham becoming father of many nations — Abraham listens. More than listens. He says “Amen” to God’s promise. He “believed” God — and the Hebrew word for “believe” eventually becomes our English word “Amen.” If God promises something, God will bring it to pass. If he created the universe out of nothing, he can call a nation into being if he sees fit to do so — even from an aged couple far too old to have a child.