Provisions are made in Scripture for the avenger of blood. The avenger of blood was the next of kin of the person who had been killed and was allowed to punish the offender, even to the point of killing the accused without being himself guilty of murder.

Reminds me of the revenge attitude of so many people today. "I don't get back, I get even." Not a very godly attitude.

Cities of refuge were to be established where a person who has accidentally killed someone could flee to and be safe. Think about all the times in Scripture that God is described as being our refuge, our safety, our shield and protector.

Jesus was very clear how He felt about a revenge kind of attitude.
Matt 5:38-39
You have heard that it was said, 'Eye for eye, and tooth for tooth.  But I tell you, Do not resist an evil person. If someone strikes you on the right cheek, turn to him the other also.

Striking on the right cheek was an insult.  Since most people are right-handed, a hit would be on the left cheek of the person being hit.  Striking on the right cheek would be a back-handed kind of hit and considered an insult.  Jesus says if someone insults you, let it go.

If we have an attitude of revenge in our hearts, we are following the crowd in doing wrong like we have been warned about before. It's so much easier to follow the crowd than to stand out in a crowd. But as Believers in Jesus, we are called to be different and to stand out!