‘Ubaydullah ibn Abi Rafi’ reported: The Haruriyya (Khawarij) came out against Ali ibn Abi Talib and they said, “There is no rule but for Allah,” (12:40). Ali, may Allah be pleased with him, said, “A word of truth by which is intended falsehood. Verily, the Messenger of Allah, peace and blessings be upon him, described some people and I recognized their description in these people. They speak the truth with their words but it does not go beyond this,” and he pointed to this throat.
Source: Ṣaḥīḥ Muslim 1066
Grade: Sahih (authentic) according to Muslim
عَنْ عُبَيْدِ اللَّهِ بْنِ أَبِي رَافِعٍ أَنَّ الْحَرُورِيَّةَ لَمَّا خَرَجَتْ وَهُوَ مَعَ عَلِيِّ بْنِ أَبِي طَالِبٍ قَالُوا لَا حُكْمَ إِلَّا لِلَّهِ قَالَ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ كَلِمَةُ حَقٍّ أُرِيدَ بِهَا بَاطِلٌ إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَصَفَ نَاسًا إِنِّي لَأَعْرِفُ صِفَتَهُمْ فِي هَؤُلَاءِ يَقُولُونَ الْحَقَّ بِأَلْسِنَتِهِمْ لَا يَجُوزُ هَذَا مِنْهُمْ وَأَشَارَ إِلَى حَلْقِهِ
1066 صحيح مسلم كتاب الزكاة باب التحريض على قتل الخوارج