Genesis 17:21 - Clarke's commentary and critical notes on the Bible

But my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year. 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.