The surah describes Sarah’s reaction to the news of her pregnancy:
"And his wife approached with a cry [of alarm] and struck her face and said, '[I am] a barren old woman!'"
The Narrative Shift: In Genesis 18:12, Sarah laughs internally out of disbelief, and Yahweh questions her, asking, "Why did Sarah laugh?" In Surah 51, her response is changed to a loud public cry and striking her face—a cultural sign of mourning or distress common in the 7th-century Near East.
The Application: You can argue that the Quran alters the psychological and theological depth of the Biblical text (where the focus is on God rebuking her lack of faith) and replaces it with anachronistic 7th-century Arab cultural expressions of shock.