Matthew 5:38-42 Go The Second Mile.
Whatever Jesus means here it is certain that he was not advocating the abrogation of this law of “an eye for an eye,” because he stated categorically that he did not come to abolish the Law or the Prophets (v. 38 Cf. 5:17; Ex. 21:24; Lev. 24:20; Dt. 19:21). This law is foundational to the principle of retributive justice in the civil sphere. The problem became that the religious leadership were advocating and endorsing this principle as an acceptable practice of vigilantism. Furthermore, “whoever slaps you” means what it still means – insult (v. 39 Cf. Lk. 6:29; Is. 50:6). It would be contrary to the very principle of the analogy of scripture to say that Jesus is repudiating defence for self, family, or country. Jesus himself instructed his disciples to take with them swords (Lk. 22:36). If they had pistols in their day, Jesus would no doubt tell them to be packing (lawfully). As to the other items here, giving someone a tunic is not giving away the farm. If one can avoid a confrontation over someone who wants to steal your jacket, then let it go (v. 40). Also, as Christians we should be prepared to “go the extra mile” if need be (v. 41). We should give as we are able (v. 42 Cf. Lk. 6:30-36).