Do Not Repay Evil with Evil
Not repaying evil for evil may come from Jesus’ teaching (Mt 5:39), although some other Jewish teachers had also recommended non-retaliation (as early as Prov 20:22). Doing what is respectable in the opinions of other people was a virtue not only to aspiring Greco-Roman politicians but also to Jewish people in their dealings with Gentiles. But while Jewish people adopted stricter guidelines than the surrounding culture for the sake of witness, they never compromised their own beliefs; the point of the admonition is to protect their witness and prevent unnecessary opposition.
Keener, C. S. (1993). The IVP Bible background commentary: New Testament (Ro 12:17–18). Downers Grove, IL: InterVarsity Press.