Charles Ellicott Commentary Matthew 5:38

"Ye have heard that it was said, An eye for an eye, and a tooth for a tooth:" — Matthew 5:38 (ASV)

An eye for an eye — Here again, the scribes first took their stand on the letter of the Law, ignoring its aim and purpose, and then expanded it in the wrong direction. As originally given, this law was a check on the “wild justice” of revenge. It established that when the balance of justice had been disturbed by an offense, the judge's role was to do no more than restore that balance, unless a further penalty was necessary to prevent crime, as in the case of theft.

In its essence, the law was a limit in both directions. It required not less than an “eye for an eye,” for a lesser penalty might lead to connivance in guilt; it also required not more, for a greater penalty would create a new injustice. The scribes, in their popular casuistry, turned this principle from a rule for judicial action into a justification for private retaliation. It was thus made to sanction a vindictive spirit that forgives nothing.