The Khawarij Heretics

Imam Abu Bakr al-Ajurri wrote 1000 years ago:

لَمْ يَخْتَلِفِ الْعُلَمَاءُ قَدِيمًا وَحَدِيثًا أَنَّ الْخَوَارِجَ قَوْمُ سُوءٍ عُصَاةٌ لِلَّهِ تَعَالَى وَلِرَسُولِهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ، وَإِنْ صَلَّوْا وَصَامُوا، وَاجْتَهَدُوا فِي الْعِبَادَةِ، فَلَيْسَ ذَلِكَ بِنَافِعٍ لَهُمْ، نَعَمْ ,
وَيُظْهِرُونَ الْأَمْرَ بِالْمَعْرُوفِ وَالنَّهْيِ عَنِ الْمُنْكَرِ، وَلَيْسَ ذَلِكَ بِنَافِعٍ لَهُمْ؛ لِأَنَّهُمْ قَوْمٌ يَتَأَوَّلُونَ الْقُرْآنَ عَلَى مَا يَهْوُونَ، وَيُمَوِّهُونَ عَلَى الْمُسْلِمِينَ
وَالْخَوَارِجُ هُمُ الشُّرَاةُ الْأَنْجَاسُ الْأَرْجَاسُ، وَمَنْ كَانَ عَلَى مَذْهَبِهِمْ مِنْ سَائِرِ الْخَوَارِجِ يَتَوَارَثُونَ هَذَا الْمَذْهَبَ قَدِيمًا وَحَدِيثًا،
وَيَخْرُجُونَ عَلَى الْأَئِمَّةِ وَالْأُمَرَاءِ وَيَسْتَحِلُّونَ قَتْلَ الْمُسْلِمِينَ

“The scholars have not disagreed about the fact that the Khawarij are evil people, disobedient to God and His Messenger.
Even if they pray, fast and perform acts of worship – none of this will benefit them.
They also show acts of commanding the good and forbidding the evil, and this will not benefit them at all, because they interpret the Qur’an according to their whims and apply it on the believers!
The Khawarij are upon an evil and filthy methodology, and the same applies to all other historic and modern day Khawarij who adopt this methodology.
They come out against the rulers and legalise the k*lling of believers.”

[“Al-Shariah”, 1/325].