The covenant of the promised Seed to come out of his loins, and of life and salvation to accrue to himself and to his posterity by virtue of that Seed; in comparison whereof God speaks slightly of all the temporal blessings conferred upon Ishmael, though in themselves they were great and glorious. By which it may sufficiently appear that Abraham's faith, whereby he is said to be justified, Romans 4:1-25, had a further reach in it than to his own immediate child, even to the Messias, whose day therefore Abraham is said to have seen, 1 Thessalonians 8:56.
Related Commentaries of Genesis 17:21
Genesis 17:21
21 But my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.