God and Guns: What the Bible Says About Self-Defense
For example, in Matthew 5:39 He said, "if someone slaps you on your right cheek..." First of all, a slap on the cheek is not a lethal attack. Second, notice that He specifically mentioned the right cheek. Most people are right-handed, so striking someone's right cheek would require a back-handed slap. That would be an insult, not a threat to your life or someone else's. Jesus was saying that you can bear insults—you don't have to retaliate. And that seems to be the general tone of the New Testament.
However, if we go to Luke 22:35-38, we see an interesting command. Jesus told His disciples to obtain a knapsack, sandals, a money bag, and a sword for their future journeys. When a disciple produced two swords, Jesus told him, "that's enough." The Greek word for "enough" is hikanos. It means "sufficient, adequate" (Bauer/Arndt/Gingrich/Danker Greek-English Lexicon, p. 374). Jesus was saying that two swords for eleven disciples (Judas had left by then) were plenty. There were lots of four-footed and two-footed varmints out there, and Jesus was giving them permission to use a weapon to defend themselves. Now, some people say that the swords here were only symbolic. If symbolic, why would Jesus speak approvingly in verse 38 of their literal interpretation? Also, if the swords were symbolic—then so were the shoes, knapsack, and money bag. But that hardly seems to fit, does it? I think here Jesus gave His followers permission to use weapons to defend themselves if they thought it would be the best option. Why else would He tell them to take a sword, along with the other items?
But what about Matthew 26:52, where Jesus told Peter to put away his sword, "for all who take the sword will perish by the sword"? It's pretty clear from the Gospels that it was Jesus' mission to die on the cross. It is equally clear that the rash Peter had a tough time understanding that and was using a weapon in the wrong way. Yes, Peter was trying to defend the innocent, but God had already revealed that it was His will for Jesus to die at that time. God has not revealed such things to us about other people today.
In fact, He has revealed that human government has the responsibility to use force to protect the innocent (Romans 13:4 again). As for the rest of us, Paul told us in 1 Timothy 5:8 that "if anyone does not provide for his own, and especially for those of his own household, he has denied the faith, and is worse than an unbeliever." What should you provide for your own household? Shelter, food, clothing, and...security. Especially in a very dangerous, fallen world, I think it is a very godly thing to provide protection (whatever level you think you are capable of) against predators and invaders.
So, back to the original question. If you see an attack upon your neighbors in progress, what should you do? I think we should do whatever is legally and morally justified to stop the attack. Armed citizens in our country can legally stop such attacks. It is not evil to defend the innocent and helpless from the evil that seeks to destroy them. I am convinced that, consistent with the Bible, defending people with force (if necessary) is one of the most loving things we can do.