Sunan Ibn Majah

Ubaidah narrated from 'Ali bin Abu Talib,:That he mentioned the Khawarij, and said: ""Among them there will be a man with a defective hand, or a short hand, or small hand. If you were to exercise restraint (i.e., not become overjoyed), I would tell you of what Allah has promised upon the lips of Muhammed for those who kill them."" I ('Ubaidah) said: ""Did you hear that from Muhammed?"" He said: ""Yes, by the Lord of the Ka'bah!' - three times