Christians get terribly confused about vengeance.
Here’s how the confusion arises. We begin by noting (rightly) that Jesus tells us not to take retribution into our hands for personal wrongs committed against us. Instead, he says, we should turn the other cheek (Mt 5:39). So far so good.
But there’s where the confusion arises. We leap from the (correct) claim that we should not exact vengeance to the (incorrect) conclusion that vengeance is itself a bad thing. As a matter of simple logic this reasoning doesn’t make sense. And it flies in the face of the teaching of Scripture.
In short, the Bible does not say, “You shouldn’t exact vengeance for personal wrongs because vengeance is a bad idea.” Rather, the Bible says, “You shouldn’t exact vengeance for personal wrongs because vengeance, though a good idea, is a complicated matter, and should therefore be left in the hands of God, who is able to sort out with perfect justice all the ins and outs of who did what to whom, and who’s really to blame for this and that, and so on.”
Thus when human beings are given (by God) the role of exacting retribution for wrongdoing, Scripture makes it clear that they are doing so as agents of God (as in Romans 13, for example – see below). And though this principle may in some circumstances be extended to other contents (a father defending his 4-year-old daughter from physical violence, perhaps?), it is not infinitely extensible, and (obviously) may not therefore be used to justify arbitrary acts of violence to avenge personal hurt feelings.
All of this and much more besides is wrapped up in Romans 12:17-13:7. Once again, note carefully, 12:19 doesn’t say, “Don’t take vengeance because that’s nasty.” Rather, it says, “Don’t take vengeance, because that’s God’s job.”
At this point, the connection to the imprecatory Psalms should be pretty clear.
