The wife of Abram, Sarai, was very beautiful, but she was barren. God later changed their names. Abram became Abraham and Sarai became Sarah. She did not give birth to her promised son, Isaac, until she was 90 years old. Genesis 11:30 tells us that Sarai was barren. In Genesis 12:11 it is said that she is beautiful. Both of these themes are repeated throughout the story of Abraham and Sarah which takes up many of the chapters of the book of Genesis.