Imaam Muhammad Ibn Saaleh Uthaymeen (rahimahullaah) said, “There is no khurooj with the sword except that it is preceded by Khurooj with the tongue”. [Ref 1]
Shaikh Saaleh Al-Fawzan (may Allaah preserve him) was asked:
The one (i.e. Dhul Khuwaysirah) who said to the Messenger (sallal-laahu-alayhi-wsallam): ‘’be just’’; is he considered to be from the Sahaabah or is he a khaarijee, alongside the fact that he did not rebel against the Messenger (sallal-laahu-alayhi-wasallam) and did not disbelieve through major (kufr etc)?
The one (i.e. Dhul Khuwaysirah) who said to the Messenger (sallal-laahu-alayhi-wasallam) ‘’be just’’ is not a just person. This was the beginning of the khawaarij in view of the fact that he accused him of oppression. And it is not a condition that the khawaarij have to carry weapons, rather he (the person) is from the khawaarij and upon their school of thought if he believes in declaring Muslims disbelievers due to major sins (they commit). If he incites (the people) against the one in charge of the affairs through sermons and writing, (then) this is the school of thought of the khawaarij even if he does not carry weapons.
The khawaarij are of different types: Amongst them are those who carry weapons; there are those who speak like the who said to the Messenger (sallal-laahu-alayhi-wasallam), ”Be Just”; amongst them are those who write and amongst them is the one who believes in his heart, but he neither speaks nor does anything; however he has the belief of the khawaarij in his creed. But some of them are worse than others. [Ref 2]
[Ref 1. Source: Quoted by Shaikh Abdullaah Al-Bukhaari (may Allaah preserve him) in ‘Sharh Fadl Ilm As-Salaf Alaa Ilm Al Khalaf- Audio Number 1. Questions & Answers section]
[Ref 2. Source: Al-Ijaabaat Al-Muhimmah Fil-Mashaakil Al-Mulimmah: page: 10-11]