Shaykh Al-Islam Ibn Taymiyyah said:
“The one who refutes the people of innovation is a Mujaahid. This is such that Yahyaa Ibn Yahyaa used to say, ‘Defending the Sunnah s more virtuous than fighting in Jihaad.‘ ” [Naqd Al-Mantiq, p.12]
Shaykh Al-Islam Ibn Taymiyyah also said:
“So whoever is a Mujaahid in the way of Allaah, by way of his tongue, then it is through commanding good and forbidding evil, explaining the religion, conveying the commands, prohibitions and good that is found in the Quraan and Sunnah, clarifying the views that contradict that, and refuting those who oppose the Quraan and the Sunnah. Or it could be by way of the hand, such as by fighting against the disbelievers.
So if he is harmed during his Jihaad by the hand or tongue of another, then his reward for that is upon Allaah. And he should not seek to return the injustice that was caused to him by the oppressor. rather is this oppressor repents and accepts the truth due to which Jihaad was made against him (in the first place), then his repentance serves to wipe away what (sin) was in the past.
“Say to those who have disbelieved, if they cease (from disbelief), their past (sins) will be forgiven. But if they return (to disbelief), then the examples of those (punished) before them have already preceded (as a warning).” [8:38]
And if he doesn’t repent and instead continues to oppose the Quraan and the Sunnah, then he is an opponent of Allaah and His Messengers. The believers have a right that is subordinate to the right of Allaah. So when this person gets punished, it is due to the right of Allaah, so that Allaah’s Word can be the highest and so that all of the religion (worship_ can be for Allaah – it is not just done for the sake of retribution.” [Al-Ihtijaaj Bil-Qadar, p.50]