Musannaf Ibn Abi Shayba 3:2635

Jarir ibn Abd al-Hamid narrated to us, from Yazid, from Abd al-Rahman ibn Abi Layla, who said: "Ghusl (ritual bathing) is on the day of Jumu'ah, the day of al-Adha, the day of al-Fitr, the day of Arafah, and the day of entering Makkah."