Genesis 17:19

17:19 God said, “No, Sarah your wife is going to bear you a son, and you will name him Isaac. ¹  I will confirm my covenant with him as a perpetual ²  covenant for his descendants after him.

Genesis 21:12

21:12 But God said to Abraham, “Do not be upset ³  about the boy or your slave wife. Do ⁴  all that Sarah is telling ⁵  you because through Isaac your descendants will be counted. ⁶ 

Romans 9:7

9:7 nor are all the children Abraham’s true descendants; rather “through Isaac will your descendants be counted.” ⁷ 

[17:19]  ¹ tn Heb “will call his name Isaac.” The name means “he laughs,” or perhaps “may he laugh” (see the note on the word “laughed” in v. 17).

[17:19]  ² tn Or “as an eternal.”

[21:12]  ³ tn Heb “Let it not be evil in your eyes.”

[21:12]  ⁴ tn Heb “listen to her voice.” The idiomatic expression means “obey; comply.” Here her advice, though harsh, is necessary and conforms to the will of God. Later (see Gen 25), when Abraham has other sons, he sends them all away as well.

[21:12]  ⁵ tn The imperfect verbal form here draws attention to an action that is underway.

[21:12]  ⁶ tn Or perhaps “will be named”; Heb “for in Isaac offspring will be called to you.” The exact meaning of the statement is not clear, but it does indicate that God’s covenantal promises to Abraham will be realized through Isaac, not Ishmael.

[9:7]  ⁷ tn Grk “be called.” The emphasis here is upon God’s divine sovereignty in choosing Isaac as the child through whom Abraham’s lineage would be counted as opposed to Ishmael.