Heb 11:11 By faith Sarah herself received power to conceive, even when she was past the age, since she considered him faithful who had promised.
God made a promise to Abraham, he needed to believe God. In the same matter we also see the importance of his wife’s faith in God. Though she was considered the weaker vessel, and though at first she doubted yet she as well needed to have faith in God.
Sarah dealing with barrenness had no point of reference to build her hope in. She was way past the age of child bearing but her strength was founded upon the faithfulness of a promising God. Far beyond the years of child bearing, yet by faith she was given natural strength to bear the child of promise. Despite moments of doubts, she held on 25 long years to conceive, perhaps strengthened by her husband’s faith. The strength of nature, as well as grace, was from God. He can make barren souls fruitful, as well as the barren wombs. Nothing is impossible for a person who does not have to do it himself for faithful is He that has promised.