It was narrated that Ibn 'Abbas (رضي الله عنه) said:

A beautiful woman used to pray behind the Messenger of Allah (ﷺ). Some of the people would go forward to stand in the front row so as not to see her, and some would lag behind to stand in the back row, and when they bowed they would look from under their armpits. Then Allah revealed concerning her the words: "To Us are known those of you who hasten forward, and those who lag behind" (al-Hijr 15:24).