do not retaliate when someone wrongs you
—My mother always taught me that if someone insults me, I should just turn the other cheek .

In the Old Testament, God told the Israelites, through Moses, that if two men were fighting and hurt a woman, the punishment was to be

life for a life, eye for eye, tooth for tooth, hand for hand, foot for foot, burn for burn, wound for wound, bruise for bruise. (Exodus 21:23-25)

The meaning of this command is that a just punishment should be equal to, and not go beyond, the crime. From this we get the phrase eye for an eye, which today is used to mean “the punishment should be as severe as the crime.” But Jesus, in the Sermon on the Mount, taught that we should not seek revenge. Instead we should “turn the other cheek”:

You have heard that it was said, “An eye for an eye and a tooth for a tooth.” But I say to you, do not resist the evildoer. But whoever strikes you on the right cheek, turn the other to him as well [whosoever shall smite thee on thy right cheek, turn to him the other also]. And if someone wants to sue you and to take your tunic, give him your coat also. And if anyone forces you to go one mile, go with him two [whosoever shall compel thee to go a mile, go with him twain]. Give to the one who asks you, and do not reject the one who wants to borrow from you. (Matthew 5:38-42)

Because their land was controlled by the Romans, the Jews of Jesus’ day had to submit to the authority of Caesar, the Roman ruler, and his soldiers. Forces you to go one mile refers to a Roman soldier making a civilian travel with him to carry his belongings. Jesus’ teaching to go with the soldier two (“twain”) miles gives us the phrase go the extra mile. It means “to do more than is necessary or expected,” as in “He not only bought my meal, but he went the extra mile and paid for my taxi ride, too.”