Here are a few options for a sentence stating that Abraham's wife in the Bible was a mother in her nineties:
* Sarah, Abraham's wife, became a mother in her nineties, a miraculous event in the Bible.
* According to the Bible, Abraham's wife, Sarah, was about ninety years old when she gave birth to Isaac.
* It is recorded in the Bible that Sarah, the wife of Abraham, conceived and gave birth to a son in her advanced age, specifically around ninety.