Not long thereafter, at Mamre, one of three angelic visitors reaffirmed that Sarah would give birth to a son. Overhearing this, “Sarah began to laugh inside herself, saying: ‘After I am worn out, shall I really have pleasure, my lord being old besides?’” Reproved for laughing, Sarah fearfully denied having done so. (Ge 18:1-15; Ro 9:9) Since Sarah is cited at Hebrews 11:11 as an example of faith, evidently her laughter was not an expression of complete unbelief but merely indicated that the thought of having a son in her old age apparently struck her as somewhat humorous. Sarah’s acknowledgment (inside herself) of Abraham as her lord was indicative of her obedience and subjection to her husbandly head, and her example is recommended to Christian wives.​—1Pe 3:5, 6.

At the age of 90, Sarah had the joy of giving birth to Isaac. She then exclaimed: “God has prepared laughter for me: everybody hearing of it will laugh at me.” Such laughter would evidently be prompted by delight and amazement over the birth of the child. Sarah nursed her son for about five years. When Isaac was finally weaned, Abraham spread a big feast. On that occasion Sarah observed Hagar’s son Ishmael, now about 19 years old, “poking fun,” or playing with Isaac in a mocking way. Apparently fearing for the future of her son Isaac, Sarah requested that Abraham dismiss Hagar and Ishmael. Abraham did so, subsequent to his receiving divine approval for this action.​—Ge 21:1-14.