Hassan bin Bilal said:"1 saw Ammar bin Yasir performing Wudu, so he went through his beard (with his hand). It was said to him" - or he said - "1 said: 'You go through your beard?' He said: 'And what is there to prevent me? Indeed I saw Allah's Messenger going through his beard
ReferencesJami' at-Tirmidhi 29In-book: Book 1, Hadith 29Source: hadith-api (fawazahmed0)