He asked Ibn Shihab about ghusl on Friday. He said: "It is a sunnah; Salim bin 'Abdullah told me, narrating from his father, that the Messenger of Allah ﷺ spoke about it from the minbar." (Using translation from Nasāʾī 1406)
أَنَّ رَسُولَ اللهِ ﷺ «تَكَلَّمَ بِهَا عَلَى الْمِنْبَرِ»