With whom did God establish His everlasting covenant in Genesis 17:19?
God established His everlasting covenant with Isaac, the son Sarah would bear, and with Isaac's seed after him. Although Abraham had asked that Ishmael might live before God, the covenant promise was directed to Isaac, as God declared in Genesis 17:19.
Les explains that in Genesis 17:18 Abraham asked God, "Oh, that Ishmael might live before thee." But God answered that Sarah would bear a son, and his name would be called Isaac. Then God said, "And I will establish my covenant with him for an everlasting covenant, and with his seed after him." Les points out that God's "I will" is a promise, and even though Abraham and Sarah may have lost sight of it, it was God's promise and would happen. The covenant line was therefore with Isaac and his seed after him, not with Ishmael as Abraham had requested.
And 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.