Who was Sarah in the Bible

Sarah was Abraham’s Wife in whose life was a recorded a miracle of giving birth at an old age. As at the time when the angels brought good news of a son (Isaac), Sarah was said to be an old barren
By faith Abraham, even though he was past age and Sarah herself was barren was enabled to become a father because he considered him faithful who had made the promise. HEBREWS 11:11
Sarah’s story is one of belief mixed with doubt. As such, she is a character to which many readers can easily relate.
Most students of the Bible are well acquainted with Sarah’s lack of faith. Her skepticism when God promised Abraham a son is understandable after all, she had more than enough reason to believe this could never happen. Sarah had aged well beyond childbearing years when God spoke to her husband for the first time. Also, Sarah and Abraham were nearly parted from each other on at least two occasions both times thanks to Abraham’s own apparent lack of faith. In strikingly
similar episodes, two rulers – first the king of Egypt, then the king of Gerar – took Sarah to be their wife. To save his own skin, Abraham had passed off Sarah as his sister (which was half true, since, in addition to being husband and wife, Sarah and Abraham were half siblings).
However, God’s plan for Sarah would not be thwarted not by outside events and not even by Sarah’s own actions. Having long since given up on the hope of bearing a son, Sarah gave her servant Hagar to Abraham, in accordance with an ancient Mesopotamian custom. This union had the desired effect: Hagar gave birth to Ishmael. But things soured when Sarah turned on Hagar.
Despite her many doubts, however, Sarah was not entirely without faith. After all, she stood by Abraham during the entire twenty-five years that transpired between the first promise and its eventual fulfillment in the birth of Isaac. She may have laughed at the thought of a son, but she did not entirely abandon hope. In fact, the prophet Isaiah held up Sarah as a model of trust in God’s faithfulness, counseling the people to “look to Abraham, your father, and to Sarah, who gave you birth” (Isaiah 51:2).
As further evidence of Sarah’s faith, it is possible to translate Hebrews 11:11 as a statement about her: “By faith even Sarah, who was past age, was enabled to bear children because she considered
him faithful who had made the promise” (see NIV footnote to Hebrews 11:11).