It was narrated from Ibrahim bin Nashit that:

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."

أَخْبَرَنَا مُحَمَّدُ بْنُ سَلَمَةَ، قَالَ حَدَّثَنَا ابْنُ وَهْبٍ، عَنْ إِبْرَاهِيمَ بْنِ نَشِيطٍ، أَنَّهُ سَأَلَ ابْنَ شِهَابٍ عَنِ الْغُسْلِ، يَوْمَ الْجُمُعَةِ فَقَالَ سُنَّةٌ وَقَدْ حَدَّثَنِي بِهِ، سَالِمُ بْنُ عَبْدِ اللَّهِ عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم تَكَلَّمَ بِهَا عَلَى الْمِنْبَرِ ‏.‏