You can’t read the Sermon on the Mount (Matt. Ch. 5 - 7) without coming away disturbed. Perhaps that’s why we don’t hear too much sermonizing based on Jesus’ longest sermon (and perhaps his only sermon recorded in the Gospels if you count Luke’s version as a different telling of the same sermon). We don’t hear many sermons based on these words because in the Sermon on the Mount, Jesus seems to be promoting what some people might call ‘works righteousness.’ Throughout the sermon, Jesus tells his hearers that God will treat them exactly how they treat others.
Jesus made it very simple for us—simple, but not necessarily easy. Jesus confirmed the Great Commandment of the Old Testament, to Love God with all our heart, mind, soul and strength, and to love our neighbours—even our enemies—as ourselves. And Jesus made it pretty clear that this is what the Judgement on the last day is all about. For, “In as much as you have done it to the least of these,” Jesus says, “you have done it unto me.”