Read Hebrews 11:11 Using Other Translations
Through faith also Sara herself received strength to conceive seed, and was delivered of a child when she was past age, because she judged him faithful who had promised.
By faith Sarah herself received power to conceive, even when she was past the age, since she considered him faithful who had promised.
It was by faith that even Sarah was able to have a child, though she was barren and was too old. She believed that God would keep his promise.