Al-Bukhari reported: Ibn Umar, may Allah be pleased with him, considered the Khawarij rebels to be the worst of Allah’s creation and he said, “Indeed, they take verses that were revealed about unbelievers and use them against believers.”
Source: Ṣaḥīḥ al-Bukhārī 6531
Grade: Sahih (authentic) according to Al-Bukhari
عن البخاري وَكَانَ ابْنُ عُمَرَ رضي الله عنه يَرَاهُمْ شِرَارَ خَلْقِ اللَّهِ وَقَالَ إِنَّهُمْ انْطَلَقُوا إِلَى آيَاتٍ نَزَلَتْ فِي الْكُفَّارِ فَجَعَلُوهَا عَلَى الْمُؤْمِنِينَ
6531 صحيح البخاري كتاب استتابة المرتدين والمعاندين وقتالهم باب قتل الخوارج والملحدين بعد إقامة الحجة عليهم