But God said, “On the contrary, Sarah your wife will bear you a son and you must name him Isaac. So I will confirm My covenant with him as an everlasting covenant for his seed after him.
Then He said, “I will most surely return to you in about a year’s time, surprisingly, Sarah your wife will have a son.” Sarah was listening at the entrance of the tent, which was behind Him.
“Then God gave Abraham the covenant of circumcision. So he became the father of Isaac and circumcised him on the eighth day, and so Isaac with Jacob, and Jacob with the twelve patriarchs.
By faith even Sarah herself received ability to conceive when she was barren and past the age, since she considered the One who had made the promise to be faithful.