Hoping against hope, he believed that he would become "the father of many nations," according to what was said, "So numerous shall your descendants be."
He did not weaken in faith when he considered his own body, which was already as good as dead (for he was about a hundred years old), or when he considered the barrenness of Sarah's womb.
References for Romans 4:19
No distrust made him waver concerning the promise of God, but he grew strong in his faith as he gave glory to God,
being fully convinced that God was able to do what he had promised.