Musnad Abu Ya'la al-Mawsili 42:69

Abu Hisham al-Rifa'i narrated to us, Ibn Fudayl narrated to us, from Salim ibn Abi Hafsa, from Atiyyah, from Abu Sa'id, that the Prophet (peace and blessings of Allah be upon him) said to Ali: "It is not lawful for anyone to be in a state of major ritual impurity (junub) in this mosque except for you and me."