Genesis 20:18--21:3

20:18 For the Lord had caused infertility to strike every woman in the household of Abimelech because he took Sarah, Abraham’s wife.

The Birth of Isaac

21:1 The Lord visited Sarah just as he had said he would and did for Sarah what he had promised. 21:2 So Sarah became pregnant and bore Abraham a son in his old age at the appointed time that God had told him. 21:3 Abraham named his son – whom Sarah bore to him – Isaac.