He laughed, through admiration and holy rejoicing at so great a blessing, not through unbelief, as Sarah did, Genesis 18:12,13, as appears from Romans 4:19,20. And though the outward act was the same in both, yet God discerned their differing dispositions and intentions therein.
Related Commentaries of Genesis 17:17
Genesis 17:17
17 Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is an hundred years old? and shall Sarah, that is ninety years old, bear?