Sunan An-Nasai, Chapter: The Book of Purification

"I was sitting with Abdullah and Abu Musa, and Abu Musa said: 'Have you not heard what 'Ammar said to Umar: 'The Messenger of Allah (saw) sent me on an errand and I became Junub, and I could not find water, so I rolled in the earth then I came to the Prophet (saw) and told him about that.' He said: 'It would have been sufficient for you to do this,' and he struck the earth with his hands, then wiped his hands, then knocked them together to remove the dust, then he wiped his right hand with his left and his left hand with his right, palm to palm, and wiped his face.'" Then Abdullah said: "Did you not see that Umar was not convinced by what 'Ammar said:" (Sahih)