Musnad Ahmad 2407

It was narrated from ‘Ikrimah that A man asked Ibn 'Abbas (رضي الله عنه) about doing ghusl on Friday: is it obligatory? He said: No, but whoever wishes may do ghusl, and I will tell you how ghusl was first prescribed. The people were poor and they used to wear wool, and they would carry water to the palm trees on their backs. The mosque of the Prophet (ﷺ) was small, with a low ceiling, so the people in their woollen garments would start to sweat. The minbar of the Prophet (ﷺ) was short; it only had three steps. So the people would sweat in their wool, and their smell and the smell of the wool would become prominent, and thus they bothered one another, until the smell reached the Messenger of Allah (ﷺ) when he was on the minbar. So he said: "O people, when you come to Jumu'ah, do ghusl and let one of you put on the best perfume he has."