Musnad Abu Ya'la al-Mawsili 140:1

Ali ibn al-Ja'd narrated to us, Sufyan al-Thawri narrated to us, from Yazid al-Raqashi, from Anas, from the Prophet (peace be upon him), who said: "Whoever performs wudu, then it is good and excellent. And whoever performs ghusl, then the ghusl is better." Meaning: on the day of Jumu'ah.