Scripture teaches us that God is not limited or hindered by the limitations of creation. God's mercy and love are not constrained by any apparent defect in creation or by any evil, whether physical evil or moral. Sarah's sterility was a physical evil, a defect that made life rather meaningless for her, a defect that could cause a woman's heart to become bitter. So Sarah laughed at the news of a son. We should not blame her if we feel her laugh was rather cynical and bitter. God's gracious providence would one day turn that laugh into genuine laughter of joy at the birth of her child.

Most of all, God is not limited by the expression of His promises. When God comes to realize any divine promise, He freely and generously gives more than the promise contained. The story of Sarah's unexpected and unhoped for pregnancy was a promise that God's love would always be a miraculous love. The promise to Sarah was the foreshadowing of a greater pregnancy. The Virgin Mary would become the mother, not of a mere mortal, but of the Son of God made flesh.