But my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.
God's announcement to Abraham regarding the promised son and the covenant to be established through him.
Genesis 17:21
King James Version (public domain)
Traditionally attributed to Moses · c. 13th century BC · The Pentateuch — Genesis, Exodus, Leviticus, Numbers, and Deuteronomy — is traditionally attributed to him
Context
19And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
20And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation.
21But my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.
22And he left off talking with him, and God went up from Abraham.
23And Abraham took Ishmael his son, and all that were born in his house, and all that were bought with his money, every male among the men of Abraham’s house; and circumcised the flesh of their foreskin in the selfsame day, as God had said unto him.