The question is clear.
Genesis 16:15. And Hagar bare Abram a son: and Abram called his son's name, which Hagar bare, Ishmael.
Genesis 21:1-3. And the Lord visited Sarah as he had said, and the Lord did unto Sarah as he had spoken. For Sarah conceived, and bare Abraham a son in his old age, at the set time of which God had spoken to him. And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac.
Galatians 4:22. For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman.
Hebrews 11:17. By faith Abraham, when he was tried, offered up Isaac: and he that had received the promises offered up his only begotten son,