Genesis 21:3

“And Abraham called the name of his son that was borne unto him, whom Sarah bare to him, Isaac.] Which is the name he was directed to give him, (<011719>Genesis 17:19); and he remembers the order, and is obedient to it; the reason of which name, which signifies laughter, was on account of his laughing for joy at the promise made him, as well as there might be afterwards a further reason for it, from Sarah’s laughing through distrust; and it might presignify the joy and laughter that would be expressed by others at his birth; and perhaps also that he would be the object of the laughter and derision of his brother; such a number of events agreeing with his name.”

“Abraham called the name of his son . . . Isaac . . . and circumcised--God was acknowledged in the name which, by divine command, was given for a memorial (compare Gen 17:19), and also in the dedication of the child by administering the seal of the covenant (compare Gen 17:10-12).”

“21:3-4 Abraham responded in faith by naming his son Isaac and circumcising him according to the terms of the covenant (see 17:9-14).”