Sahih Bukhari Volume 009, Book 088, Hadith Number 222.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 88. Afflictions and the End of the War
Narrated By Abu Wail : Abu Musa and Abii Mas'ud went to 'Ammar when 'Ali had sent him to Kufa to exhort them to fight (on 'Ali's side). They said to him, "Since you have become a Muslim, we have never seen you doing a deed more criticizable to us than your haste in this matter." 'Ammar said, "Since you (both) became Muslims, I have never seen you doing a deed more criticizable to me than your keeping away from this matter." Then Abu Mas'ud provided 'Ammar and Abu Musa with two-piece outfits to wear, and one of them went to the mosque (of Kufa).