Refusing to leave well-enough alone, I want to take a look a bit further down Chapter 5 of the Gospel of St. Matthew. After the Beatitudes, with a short interlude on salt and light, we have a long list of sayings, using the formula "You have heard it said . . . but I say to you . . ." This series of sayings is prefaced by Jesus' insistence that he is not abolishing the Law, but fulfilling the Law. I think it important to keep that in mind as we consider this whole series.
One thing it is important to remember is that Jesus is saying all this on his own authority. Pronouncing upon the law was the role of learned teachers; Jesus is insisting he is one. Further, this authority of the Teacher was considered to be something granted by God alone; Jesus is insisting that he has Divine imprimatur for these teachings.
The "You have heard it said . . ." sayings deal with specific commandments: murder, adultery, and issues surrounding the legal practices of the people, including civil complaints, divorce, the rule of vengeance, and creating distinctions of "friend" and "enemy". All of them deal with how we are to live together as a people who proclaim the God of creation and redemption as their sole King. The King in his Court was the sole arbiter of true justice; here, Jesus is telling us that justice is not confined to a simple-minded literal understanding of words like "murder", "adultery", and that Divine favor is not limited to arbitrary distinctions like "friend" and "enemy". As the ekklesia, those called out to be a people different than others, we are a people whose life together is determined by a God of bounteous love and prodigal grace. Murder is not just taking a life; it is destruction of the communal bonds that hold us all together. Adultery is not just marital infidelity, but a surrender to physical desire that breaks the bonds of family that keep the community growing. Divorce might seem like a necessary evil, but it perpetuates the breaking of communal ties that bind us together. Enmity is an artificial category; we are all the recipients of God's grace and forbearance, and therefore entitled to all the love we can share with one another. The false distinctions between friend and enemy are just another way of destroying the communal bonds, a way we divide what God has not only called together, but called to be apart together.
One caveat, I think is necessary. Once again, while it might seem on a cursory reading that Jesus is here setting out all sorts of rules we are obliged to follow, otherwise facing eternal condemnation, I think that the context in which Jesus is offering this set of sayings belies such an interpretation. Remember, Jesus is heightening and tightening the demands placed upon the people who desire to be called God's people. These are not simple rules of personal moral virtue, but a set of understandings within a body of people. They are not rules for living; they are rules for living together. Jesus is insisting that, if we going to be the people of God, we have to live that way. Not just ensuring our adherence to the letter of the Law, but living in the Spirit of the law.
Again, I just don't know how someone could imagine that we liberals would find something not to like about this. Unless, of course, there are liberal Christians who think murder, hatred, enmity, sexual promiscuity, and the general destruction of communal ties is OK.