http://www.gotquestions.org/revenge-vengeance.html
There are only two times in the Bible when God gives men permission to avenge in His name. First, after the Midianites committed hideous, violent acts against the Israelites, the cup of God’s wrath against the Midianites was full, and He commanded Moses to lead the people in a holy war against them. “The LORD said to Moses, ‘Take vengeance on the Midianites for the Israelites. After that, you will be gathered to your people’" (
Numbers 31:1-2). Here, again, Moses did not act on his own; he was merely an instrument to carry out God’s perfect plan under His guidance and instruction. Second, Christians are to be in submission to the rulers God has set over us because they are His instruments for “vengeance on evildoers” (
1 Peter 2:13-14). As in Moses’ case, these rulers are not to act on their own, but are to carry out God’s will for the punishment of the wicked.
It is tempting to try to take on the role of God and seek to punish those who we feel deserve it. But because we are sinful creatures, it is impossible for us to take revenge with pure motives. This is why the Mosaic Law contains the command “Do not seek revenge or bear a grudge against one of your people, but love your neighbor as yourself. I am the LORD” (
Leviticus. 19:18). Even David, a “man after God’s own heart” (
1 Samuel 13:14), refused to take revenge on Saul, even though David was the innocent party being wronged. David submitted to God's command to forego vengeance and trust in Him: “May the LORD judge between you and me. And may the LORD avenge the wrongs you have done to me, but my hand will not touch you (
1 Samuel 24:12).
As Christians, we are to follow the Lord Jesus’ command to “love your enemies and pray for those who persecute you” (
Matthew 5:44), leaving the vengeance to God.