Genesis 17:1-4, 17-19

When Abram was ninety-nine years old, the LORD appeared to him and said, “I am God Almighty; Walk [habitually] before Me [with integrity, knowing that you are always in My presence], and be blameless and complete [in obedience to Me]. “I will establish My covenant (everlasting promise) between Me and you, And I will multiply you exceedingly [through your descendants].” Then Abram fell on his face [in worship], and God spoke with him, saying, “As for Me, behold, My covenant is with you, And [as a result] you shall be the father of many nations.

Then Abraham fell on his face and laughed, and said in his heart, “Shall a child be born to a man who is a hundred years old? And shall Sarah, who is ninety years old, bear a child?” And Abraham said to God, “Oh, that Ishmael [my firstborn] might live before You!” But God said, “No, Sarah your wife shall bear you a son indeed, and you shall name him Isaac (laughter); and I will establish My covenant with him for an everlasting covenant and with his descendants after him.