Sunan Ibn Majah, Book 1, Hadith 172 (In-Book) ⓘ

'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."

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا إِسْمَاعِيلُ ابْنُ عُلَيَّةَ، عَنْ أَيُّوبَ، عَنْ مُحَمَّدِ بْنِ سِيرِينَ، عَنْ عَبِيدَةَ، عَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ، قَالَ وَذَكَرَ الْخَوَارِجَ فَقَالَ فِيهِمْ رَجُلٌ مُخْدَجُ الْيَدِ أَوْ مُودَنُ الْيَدِ أَوْ مُثْدَنُ الْيَدِ وَلَوْلاَ أَنْ تَبْطَرُوا لَحَدَّثْتُكُمْ بِمَا وَعَدَ اللَّهُ الَّذِينَ يَقْتُلُونَهُمْ عَلَى لِسَانِ مُحَمَّدٍ ـ صلى الله عليه وسلم ـ ‏.‏ قُلْتُ أَنْتَ سَمِعْتَهُ مِنْ مُحَمَّدٍ ـ صلى الله عليه وسلم ـ قَالَ إِي وَرَبِّ الْكَعْبَةِ ‏.‏ ثَلاَثَ مَرَّاتٍ ‏.‏