1When Abram was ninety-nine years old, Yahweh appeared to Abram and said to him, “I am God Almighty. Walk before me and be blameless. 2I will make my covenant between me and you, and will multiply you exceedingly.”
3Abram fell on his face. God talked with him, saying, 4“As for me, behold, my covenant is with you. You will be the father of a multitude of nations. 5Your name will no more be called Abram, but your name will be Abraham; for I have made you the father of a multitude of nations. 6I will make you exceedingly fruitful, and I will make nations of you. Kings will come out of you. 7I will establish my covenant between me and you and your offspring after you throughout their generations for an everlasting covenant, to be a God to you and to your offspring after you. 8I will give to you, and to your offspring after you, the land where you are traveling, all the land of Canaan, for an everlasting possession. I will be their God.”
9God said to Abraham, “As for you, you shall keep my covenant, you and your offspring after you throughout their generations. 10This is my covenant, which you shall keep, between me and you and your offspring after you. Every male among you shall be circumcised. 11You shall be circumcised in the flesh of your foreskin. It will be a token of the covenant between me and you. 12He who is eight days old shall be circumcised among you, every male throughout your generations, he who is born in the house, or bought with money from any foreigner who is not of your offspring. 13He who is born in your house, and he who is bought with your money, must be circumcised. My covenant shall be in your flesh for an everlasting covenant. 14The uncircumcised male who is not circumcised in the flesh of his foreskin, that soul shall be cut off from his people. He has broken my covenant.”
15God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but her name shall be Sarah. 16I will bless her, and moreover I will give you a son by her. Yes, I will bless her, and she will be a mother of nations. Kings of peoples will come from her.”
17Then Abraham fell on his face, and laughed, and said in his heart, “Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?” 18Abraham said to God, “Oh that Ishmael might live before you!”
19God said, “No, but Sarah, your wife, will bear you a son. You shall call his name Isaac. I will establish my covenant with him for an everlasting covenant for his offspring after him. 20As for Ishmael, I have heard you. Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly. He will become the father of twelve princes, and I will make him a great nation. 21But I will establish my covenant with Isaac, whom Sarah will bear to you at this set time next year.”
22When he finished talking with him, God went up from Abraham. 23Abraham took Ishmael his son, all who were born in his house, and all who were bought with his money: every male among the men of Abraham’s house, and circumcised the flesh of their foreskin in the same day, as God had said to him. 24Abraham was ninety-nine years old when he was circumcised in the flesh of his foreskin. 25Ishmael, his son, was thirteen years old when he was circumcised in the flesh of his foreskin. 26In the same day both Abraham and Ishmael, his son, were circumcised. 27All the men of his house, those born in the house, and those bought with money from a foreigner, were circumcised with him.
Isaac was the son of promise to Abraham and Sarah, and the half-brother of Ishmael (who became the father of the Arab people) and the father of Esau (from whom came the Edomites) and Jacob. Isaac was born of a mother beyond childbearing age by a miracle of Yahweh, and was a focus of the testing of Abraham and Sarah, his parents.
The name Isaac means "to laugh, or he laughs," which is based on the response of Sarah to Yahweh's statement to Abraham that she was to bear a son. Sarah was hiding out of sight when this announcement was made by the Angel of Yahweh, and upon hearing this statement, she laughed, which she denied later before the angel. Such an idea was considered impossible but happened as promised by the heavenly visitor. Later, Abraham's faith was tested when God commanded him to sacrifice his only son, Isaac. He followed through with this command of God but received him back alive, since Yahweh kept him from doing so, declaring that now He knew by experience (see the meaning of Hebrew yada') that Abram did not withhold his son.
Later in Isaac's life, he married Rebekah, who bore him Jacob (biography) and Esau (his favorite), and was tricked by Jacob and Rebekah into giving his younger son Jacob his blessing.
Isaac was the only son of Abraham and Sarah, a half-brother of Ishmael and father of Esau and Jacob. Isaac was born when both of his parents were very old, the circumstances surrounding his birth being a test of their faith. The meaning of Isaac's name (“he laughs”) is explained by the fact that Abraham laughed when he was told a son would be born to him at the age of a hundred. Abraham's faith was further tested when he was told to sacrifice Isaac but was stopped at the last moment from carrying out this instruction.
See also Biographies of Bible Characters, People and Characters in the Bible.