Musnad Abu Ya'la al-Mawsili 153:115

Ishaq ibn Abi Isra'il narrated to us, Sufyan narrated to us, from al-Zuhri, from Salim, from his father, who said: I heard the Prophet, may Allah bless him and grant him peace, saying upon the pulpit: "Whoever among you comes to the Friday [prayer], let him perform ghusl (ritual bath)."