Musnad Ahmad

It is narrated from Hazrat Abu Hurairah (may Allah be pleased with him) that once, while I was in a state of impurity, I met the Noble Prophet (peace and blessings be upon him). I continued walking with the Noble Prophet (peace and blessings be upon him) until he sat down at a place. Taking the opportunity, I slipped away from behind and went to my tent, performed ghusl (ritual bath), and then returned to the presence of the Prophet. The Noble Prophet (peace and blessings be upon him) was still sitting there. Upon seeing me, he asked, "Where did you go?" I replied, "When I met you, I was in a state of impurity. I did not feel it appropriate to sit with you in that state, so I left and performed ghusl (and have now come back to your service)." The Noble Prophet (peace and blessings be upon him) said, "A believer does not become impure."