When is it appropriate to engage in combat, to take up arms, to inflict harm? Is there a time to fight? to the death if necessary? Does God require us to be passive in the face of evil and malevolence?
If God ever taught anyone to fight, and He did (Ps 144:1), then there’s a time for fighting, a time for engaging in warfare. (Ec 3:8) When is that, and who should we be willing to fight?
It’s a soldier’s job to fight to the death, and we find many godly soldiers in scripture. (Ac 10:22) What’s unique about soldiers is that they’re under a governor or a king; their combat is subject to civil authority. (Jn 18:36)
In a private context, fighting to defend yourself and loved ones is generally permitted by civil authority; this is common moral understanding and it’s grounded in Torah. (Ex 22:2) Under such conditions it’s right to fight in self-defense, when physical safety is at risk.
But taking up arms to avenge a death (De 19:12), or to put down rioters, looters and anarchists, depends on the attitude of civil authority. Does local government want your assistance? Or at least not disapprove of it? If so, then cooperate as you’re able. If not, stand down, love your enemies and pray for them, seeking their welfare (Mt 5:44), looking to God to intervene with justice in His time. (Ps 119:84)
Herein lies a key difference between Christianity and Islam: Jehovah forbids taking the law — even the divine law — into our own hands (Ro 12:19), and deciding for ourselves when and how to put away evil (Ex 22:3); this is the duty of civil government (Ro 13:4), not the individual. (Ex 20:13) On the other hand, according to Islam, Allah commends killing infidels apart from civil authority, which is what makes Islam so dangerous.
God forbids avenging ourselves and others, righting perceived wrongs on our own, because when we’re offended our judgement is clouded and it’s virtually impossible for us to dispense justice. We can’t know exactly what another person deserves for what they’ve done; this requires knowing their heart and motives, and that’s entirely beyond our reach.
And even if we did know someone’s exact motivation, God has given us little indication how to precisely measure the degree of immorality of any given behavior, or to determine an appropriate ultimate punishment. In fact, God expressly forbids individuals from doing this. (Mt 7:1) His Law only gives civil authority the right to formally assess guilt, and to impose prescribed consequences for specific types of crimes, but even then He’s generally more concerned about cleansing society of willful evil doers (De 17:12) and discouraging rebellion (13) than actually administering justice.
The job of formally righting all wrongs belongs to God Himself, and not to Man (Ro 2:2), and God isn’t doing that just yet (Ec 8:11); He’s prepared a Day in which He’ll begin administring full justice (Ro 2:5-6), and His timing will be perfect.
Meanwhile, when it’s time to defend ourselves, we must do so benevolently, in love (1Co 16:14) — using only minimal necessary force to protect ourselves and others from malevolence, all the while esteeming others better than ourselves and praying for those who would abuse us. (Php 2:3) All other forms of strife, wrath and anger are forbidden. (Ep 4:31-32) So, when we find malice lingering in our hearts, harboring a desire to inflict harm or see evil punished (Pr 24:17-18), it’s time to step back and examine ourselves; our wrath does not work God’s righteousness. (Ja 1:20)