But my covenant I will establish with Isaac, whom Sara shall bring forth to thee at this time in the next year.

But my covenant will I establish with Isaac, whom Sarah shall bear to thee at this appointed time in the next year.

But my agreement will be with Isaac, to whom Sarah will give birth a year from this time.

Yet in truth, I will establish my covenant with Isaac, to whom Sarah will give birth for you at this time next year."

Et pactum meum statuam cum Isaac, quem pariet tibi Sarah in tempore hoc, anno altero.

My covenant will I establish with Isaac - All temporal good things are promised to Ishmael and his posterity, but the establishment of the Lord's covenant is to be with Isaac. Hence it is fully evident that this covenant referred chiefly to spiritual things - to the Messiah, and the salvation which should be brought to both Jews and Gentiles by his incarnation, death, and glorification.

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.

He names that child, Isaac - Laughter, because Abraham rejoiced in spirit when this son was promised him.