Romans 4:22-25, Is Anything Too Hard for the Lord?
As Jesus said, “With men this is impossible; but with God all things are possible.” (Matt.19:26; Mark 10:27; Luke 18:27) Sarah laughed at the thought. It reflected her unbelief (Gen. 18:13, 15). God asked Abraham why did Sarah laugh? God answered to quell all doubt, “Is any thing too hard for the LORD? At the time appointed I will return unto thee, according to the time of life, and Sarah shall have a son.” (Gen. 18:14).
Abraham believed God and it was counted to him for righteousness. The gospel likewise is to be understood by faith.