Genesis 17:21

21 and My covenant I establish with Isaac, whom Sarah doth bear to thee at this appointed time in the next year;'

Genesis 17:21 Meaning and Commentary

Genesis 17:21

But my covenant will one establish with Isaac
The covenant of circumcision; for though Ishmael was circumcised, and his posterity practised that rite, yet it was not enjoined them of God; nor was it to them, or served the same purpose as to the Israelites; and particularly the promise of the land of Canaan, made in that covenant, belonged only to the posterity of Isaac, and to those only in the line of Jacob, and especially that of the Messiah springing from him, which circumcision had a respect unto:

whom Sarah shall bear unto thee, at this set time, in the next year:
that is, at the end of nine months, which is the set time a woman goes with child.

Genesis 17:21 In-Context

19 and God saith, `Sarah thy wife is certainly bearing a son to thee, and thou hast called his name Isaac, and I have established My covenant with him, for a covenant age-during, to his seed after him.

20 As to Ishmael, I have heard thee; lo, I have blessed him, and made him fruitful, and multiplied him, very exceedingly; twelve princes doth he beget, and I have made him become a great nation;

21 and My covenant I establish with Isaac, whom Sarah doth bear to thee at this appointed time in the next year;'

22 and He finisheth speaking with him, and God goeth up from Abraham.

23 And Abraham taketh Ishmael his son, and all those born in his house, and all those bought with his money -- every male among the men of Abraham's house -- and circumciseth the flesh of their foreskin, in this self-same day, as God hath spoken with him.