Musnad Ahmad 30:1847

Muhammad ibn Abi ‘Adi narrated to us, from Humayd, from Bakr, from Abu Rafi‘, from Abu Hurayrah, who said: I met the Prophet, peace and blessings of Allah be upon him, while I was in a state of major ritual impurity (junub). I walked with him until he sat down, then I slipped away and went to my place, where I performed ghusl (ritual bath). Then I returned while he was still sitting. He said: "Where were you?" I said: "You met me while I was in a state of major ritual impurity, and I disliked sitting with you while I was in that state, so I went and performed ghusl." He said: "Subhan Allah (Glory be to Allah), indeed, the believer does not become impure."