Knowing The Word in Genesis 17:15-27, Isaac's Birth Promised

15 And God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name [an alternative pronunciation, both names mean “princess’”]. 16 I will bless her [first promise of God’s blessing on her], and moreover, I will give you a son by her. I will bless her, and she shall become nations; kings of peoples shall come from her.” [God sees in their relationship a true one-flesh marriage.] 17 Then Abraham fell on his face [a gesture of awe and amazement] and laughed [in Hebrew spells Isaac, confirming the promise unwittingly in his response] and said to himself, “Shall a child be born to a man who is a hundred years old? Shall Sarah, who is ninety years old, bear a child?” 18 And Abraham said to God, “Oh that Ishmael might live before you!” [Abraham is showing his reservations. Would you?] 19 God said, “No [God rebukes Abraham’s doubt emphatically], but Sarah your wife shall bear you a son, and you shall call his name Isaac. I will establish my covenant with him [by implication excluding Ishmael] as an everlasting covenant for his offspring after him. 20 As for Ishmael, I have heard you [the meaning of Ishmael]; behold, I have blessed him and will make him fruitful and multiply him greatly. He shall father twelve princes, and I will make him into a great nation. 21 But I will establish my covenant with Isaac, whom Sarah shall bear to you at this time next year.”

22 When he had finished talking with him, God went up from Abraham. 23 Then Abraham took Ishmael his son and all those born in his house or bought with his money, every male among the men of Abraham's house, and he circumcised the flesh of their foreskins that very day, as God had said to him. [Abraham responds in immediate obedience.] 24 Abraham was ninety-nine years old when he was circumcised in the flesh of his foreskin. 25 And Ishmael his son was thirteen years old when he was circumcised in the flesh of his foreskin. 26 That very day Abraham and his son Ishmael were circumcised. 27 And all the men of his house, those born in the house and those bought with money from a foreigner, were circumcised with him.