Galatians 4:23
But we see that the child of the slave-girl was born in the common course of nature; but the child of the free woman in fulfilment of the promise.
Hebrews 11:11
Through faith even Sarah herself received strength to become a mother--although she was past the time of life for this--because she judged Him faithful who had given the promise.
Romans 9:7-8
nor because they are Abraham's true children. But the promise was "Through Isaac shall your posterity be reckoned."
Romans 4:18-21
Under utterly hopeless circumstances he hopefully believed, so that he might become the forefather of many nations, in agreement with the words "Equally numerous shall your posterity be."
Romans 10:8
But what does it say? "The Message is close to you, in your mouth and in your heart;" that is, the Message which we are publishing about the faith--
Galatians 4:28-29
But you, brethren, like Isaac, are children born in fulfilment of a promise.