Your sermon should encourage God’s people to do good to everyone in response to God’s grace and as a reflection of God’s character. This must the emphasis of your preaching since this is the fundamental message that Jesus sought to convey in the final section of Matthew 5:1–48.
Along with emphasizing our attitude toward other people, your sermon can also touch on the changes between the new covenant and the old covenant. It migfht be best to do two separate sermons rather than one, if you think that the content to be covered is too much for one sermon.
38 “You have heard that it was said, ‘An eye for an eye and a tooth for a tooth.’