1 Thessalonians 5:15

See that none render unto any one evil for evil; but always follow after that which is good, one toward another, and toward all.

None render unto any one evil for evil ... This has no reference whatever to magistrates whose duty it is to mete out punishment to convicted criminals. Rather the teaching here is that Christians must not, in their personal relationships, retaliate in kind against wrong-doers. Christianity was never intended merely for clear days and fair weather. In the bitter experiences of life, the grace of non-retaliation must be honored and cultivated, difficult as it may be to do so.

Paul said almost this same thing in Romans 12:17, under which additional comment on this may be found in my Commentary on Romans, p. 439.