38 “You have heard that it was said, ‘An eye for an eye and a tooth for a tooth.’ 39 But I say to you, Do not resist the one who is evil. But if anyone slaps you on the right cheek, turn to him the other also. 40 And if anyone would sue you and take your tunic, let him have your cloak as well. 41 And if anyone forces you to go one mile, go with him two miles. 42 Give to the one who begs from you, and do not refuse the one who would borrow from you. – Matthew 5:38-42
To understand this saying correctly, one must note that Jesus does not cite the words “an eye for an eye and a tooth for a tooth” directly from the Old Testament, for in that case he would certainly have introduced it with the formula “it is written.” But he cites it in the way it had from ancient times been taught and explained in Jewish schools and opposes the false interpretation that had been given of it. And that false interpretation did not consist in the fact that people considered the law of retribution as taught in the Old Testament also applicable in private life and mutual interactions, but that publicly as well, before a judge, they made it a tool of self-interest, personal vengeance, and hatred. Jesus, opposing this abuse, offers in its place the principle of love and patience. His disciples must not resist one who is evil, that is, they must not (according to the rule “an eye for an eye and a tooth for a tooth”) return evil for evil. They must not counter an unfair demand of their neighbor with an equally unfair demand of their own. They must not attempt to avenge themselves on their neighbor with like conduct but rather seek to win him with love, patience, long-suffering, leniency, and a spirit of accommodation. In saying this, however, Christ is absolutely not condemning every instance of defending one’s own rights. For when one of the officers in the high priest’s hall of justice struck Jesus, Jesus does not turn the other cheek but defends himself, saying: “If I have spoken wrongly, testify to the wrong. But if I have spoken rightly, why do you strike me?” (John 18:22–23; also cf. Paul, Acts 22:25; 23:3; 25:10). But the rights of others as well as our own must, according to Christ, be esteemed so highly that they may not in any way be subordinated to personal vindictiveness, hatred, self-interest, to the evil tendencies of the human heart. When we fight for them, we must do so out of love for God and our neighbor. Vengeance and recompense, also according to the Old Testament, are the Lord’s own cause (Deut. 32:35).
Reformed Dogmatics Volume 3: Sin and Salvation in Christ (Grand Rapids, MI; Baker Academic; 2006) p. 161-162.