Williams(i)
16 So it is conditioned on faith, that it might be in accordance with God's unmerited favor, so that the promise might be in force for all the descendants of Abraham, not only for those who belong to the law party but also for those who belong to the faith group of Abraham. He is the father of us all,
17 as the Scripture says, "I have made you the father of many nations." That is, the promise is in force in the sight of God in whom he put his faith, the God who can bring the dead to life and can call to Himself the things that do not exist as though they did.
18 Abraham, building on hope in spite of hopeless circumstances, had faith, and so he actually became the father of many nations, just as it had been told him, "So numberless shall your descendants be."