答:這裡是在講不要在法庭上尋求報復。舊約的律法在某個層面上，是為了人心的剛硬而設的 (正如摩西設立休書，不是說離婚是神喜悅的，見太19：3-12)。舊約規定以眼還眼，以牙還牙，是為了不要報復過分，給法官一個斷案的原則。但神真正的的心意要在耶穌基督身上才顯明，是要愛我們的仇敵。新約愛的律法已經取代舊約報復的律法。

請參考EBC的解釋：
39 Jesus' disciple is not to resist "an evil person" (to ponero could not easily be taken to refer here to the Devil or to evil in the abstract). In the context of the lex talionis, the most natural way of understanding the resistance is "do not resist in a court of law." This interpretation is required in the second example (v. 40). As in vv. 33-37, therefore, Jesus' teaching formally contradicts the OT law. But in the context of vv. 17-20, what Jesus is saying is reasonably clear: the OT, including the lex talionis, points forward to Jesus and his teaching. But like the OT laws permit ting divorce, enacted because of the hardness of men's hearts (19:3-12), the lex talionis was instituted to curb evil because of the hardness of men's hearts. "God gives by concession a legal regulation as a dam against the river of violence which flows from man's evil heart" (Piper, p. 90).
As this legal principle is overtaken by that toward which it points, so also is this hardness of heart. The OT prophets foretold a time when there would be a change of heart among God's people, living under a new covenant (Jer 31:31-34; 32:37-41; Ezek 36:26). Not only would the sins of the people be forgiven (Jer 31:34; Ezek 36:25), but obedience to God would spring from the heart (Jer 31:33; Ezek 36:27) as the eschatological age dawned. Thus Jesus' instruction on these matters is grounded in eschatology. In Jesus and the kingdom, fulfillment (even if partial) of the OT promises, the eschatological age that the Law and Prophets had prophesied (11:13) arrives; and the prophecies that curbed evil while pointing forward to the eschaton are now superseded by the new age and the new hearts it brings (cf. Piper, pp. 89-91).
Four illustrations clarify Jesus' point and drive it home. In the first, a man strikes another on the cheek--not only a painful blow, but a gross insult (cf. 2Cor 11:20). If a right-handed person strikes someone's right cheek, presumably it is a slap by the back of the hand, probably considered more insulting than a slap by the open palm (cf. M Baba Kamma 8:6). The verb "strikes" (rhapizei) probably refers to a sharp slap. Many commentators contrast Luke's typto ("strikes," Luke 6:29), arguing the latter refers to blows with a rod--i.e., Luke deals not with insult but with pain and damage. The contrast is false; the semantic overlap between the two verbs is substantial, and typto can refer to a slap (e.g., Acts 23:3). But instead of seeking recompense at law under the lex talionis, Jesus' disciples will gladly endure the insult again. (There are overtones of Isa 50:6 here, applied in Matt 26:67 to Jesus; cf. Gundry, Use of OT, pp. 72-73.)