Muwatta Malik:Jumu'a:Hadith 228
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ صَفْوَانَ بْنِ سُلَيْمٍ، عَنْ عَطَاءِ بْنِ يَسَارٍ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ غُسْلُ يَوْمِ الْجُمُعَةِ وَاجِبٌ عَلَى كُلِّ مُحْتَلِمٍ ‏"‏ ‏.‏

Yahya related to me from Malik from Safwan ibn Sulaym from Ata ibn Yasar from Abu Said al-Khudri that the Messenger of Allah, may Allah bless him and grant him peace, said, “Ghusl on the day of jumua is incumbent on every male who has reached puberty.”