Quite simply the best commentary I have ever read, check that, the best commentary I am still in the process of reading and reviewing is R.T. France's The Gospel of Matthew (NICNT; Eerdmans). This is just one example of what I am impressed with, check out his comments on Mt 5:38-42 which he labels "Retribution":
Here more than anywhere in this section we need to remind ourselves that Jesus' aim is not to establish a new and more demanding set of rules to supplant those of the scribes and Pharisees. It is to establish a 'greater righteousness,' a different understanding of how we should live as the people of God, an alternative set of values. In place of the principle of retribution he sets nonresistance; in place of the defense of legal rights he sets uncalculating generosity; in place of concern for oneself he sets concern for the other. The disciple may be forced to conclude that in an imperfect human society Jesus' illustrations of these principles could not work as literal rules of conduct, that unlimited generosity to beggars would not only undermine the economic order but also in the end do no good to the beggars themselves. But instead of therefore dismissing Jesus' teaching as starry-eyed utopianism, a proper response to this challenging section is to ask in what practical ways Jesus' radical principles can be set to work in our very different world. Our answers will vary, but if they are true to Jesus' teaching they will represent an essentially non-self-centered approach to ethics which puts the interests of the other before personal rights or convenience. We should note also, however, that a willingness to forgo one's rights and even to allow oneself to be insulted and imposed on is not incompatible with a firm stand for justice in principle and for the rights of others. (217-218)
This is just part of the introduction to the section(217-218), before the verse-by-verse exegesis! (219-222)
I have found this commentary to be intellectually stimulating, but one also that gives pause for reflection and self-inventory and highly recommend it without reservations. 'A commentary you cannot put down' is the best compliment I can give it!