Introduction
Sarah, originally named Sarai, is the wife of Abraham and mother of Isaac, described according to Genesis 20:12 as Abraham's half-sister, sharing the same father, Terah, but a different mother. Her long childlessness, and her eventual, unexpected pregnancy in old age, is central to the unfolding of God's covenant promise to Abraham.
Family
Childlessness and Hagar
Sarah remained childless for decades of her marriage to Abraham. Following the custom of the time, she gave her Egyptian servant Hagar to Abraham as a surrogate wife, and Hagar bore Ishmael, though the arrangement led to tension between the two women.
The promise and Isaac's birth
When three visitors (understood in the text as representing God) told Abraham that Sarah would bear a son within the year, Sarah, listening at the tent entrance, laughed to herself at the improbability, given her age; when questioned, she denied laughing, out of fear. She later bore Isaac, whose name means "he laughs", a name connected in the text to this episode.
In foreign courts
On two separate occasions (in Egypt with Pharaoh, and later in Gerar with King Abimelech), Abraham, fearing for his own safety, presented Sarah as his sister rather than his wife, a half-truth the text explains through her being his father's daughter by a different mother, leading to complications resolved by divine intervention in both cases.
Death
Genesis records Sarah's death at age 127 in Hebron, and Abraham's negotiation to purchase the cave of Machpelah from the Hittites as a burial site for her, an account given in unusual detail for the death of any figure in Genesis.