Recently I've been reading through Scot McKnight's Sermon on the Mount: The Story of God Bible Commentary. This is a book that I received for Christmas and have slowly been working my way through it passage by passage. It is one of the best books that I have read in the last year and one that I highly recommend.
This excerpt from the book shows the centrality of love as the ethic of Jesus.
Jesus forms an antithesis: first, he gives his prescribed behavior (5:44 - love your enemies, pray for your persecutors); second, he grounds the love-your-enemy command in the universal love of God for all humans (5:45). Third, Jesus interrogates his followers by pushing back against an ethnic-family-only kind of love. That sort of biased makes them no different than the tax collectors and Gentiles (5:46-47). Finally, he offers a summary statement: "Be perfect." But this summary makes sense only by perceiving the logic of 5:44-45: as God cares for all, so they are to love all; as God is perfect, so they are to be perfect (5:48).
Jesus' fundamental strategy for enemies was to make them our neighbors, and the concrete form of Jesus' enemy love was to invite them to his table - so that at the table of Jesus we find typical "enemies" like tax collectors and sinners.(Scot McKnight, Sermon on the Mount: The Story of God Bible Commentary)