Having looked the Beatitudes as the introduction to the Sermon on the Mount I'd like to look at some of the key teachings of the remainder of the sermon.
First we should note the structure of many of the sayings in this sermon. Understanding the structure is important because we can otherwise easily misinterpret them.
Six of the sayings begin with the words "You have heard that it was said ..." and go on to say "but I tell you ..."
This immediately poses a problem for us, because some of them are direct quotations from the Law of Moses, or an allusion to a Mosaic law. The Law of Moses was the Law of God, so Jesus was in effect saying "you have heard it was said [by God] ... but I say ..." - He appears to be presuming to change, correct or add to the Law of God! If so, it's amazing that no one in the crowd seems to have been shocked or asked on what authority He was altering the Law of God.
The second problem is that if the Law of Moses wasn't onerous enough, Jesus now appears to be making it even more difficult to please God. The Law had said "don't murder", and that commandment would have been easy enough for a lot of people to keep, but if "don't be angry" becomes a commandment with equal force, then many more people become law-breakers. Indeed, a law that may have seemed difficult to keep would now become almost impossible. Even Jesus got angry (Mark 3:5) and called people fools (Matt 23:17) which would contradict His own commandment and make Him a sinner!
Is that what Jesus intended? Did He intend to replace the Law of Moses with an even more difficult law? Is he saying that if anyone missed the point that they couldn't be saved by law-keeping that He would now give them a law which would completely dash their hopes of being obedient or pleasing God? If so, then these six sayings would run counter to so much of His teaching about the graciousness of God and His generosity in "giving" the Kingdom to people who who previously been excluded from the community of God's people.
So what did He intend?
These problems are created because interpreters often make the mistake of seeing them as sayings in two parts (i.e. a dyadic pattern):
1. You have heard ...
2. But I tell you
The sayings then become hard sayings containing high ideals and making impossible demands.
In fact, five of these six these sayings are in three parts (triadic) and are followed by a statement beginning with "so ..." or "therefore". These statements are often seen as illustrations tacked on to the 'new' commandment. However, in the Greek the second parts all use participles describing an ongoing action and the third part ("so/therefore") are all imperatives.
The third part of these sayings are not merely illustrations - they are in fact the climax of the teaching. In Biblical teaching the third element of a teaching is where the climax regularly comes and Matthew's Gospel has about 27 teachings with a threefold or triadic pattern, with 14 of them in the Sermon on the Mount (see Stassen and Gushee, Kingdom Ethics).
The threefold pattern in these five sayings then becomes a statement of a commandment given through Moses or a traditional approach to righteousness, followed by a comment by Jesus about the root causes of failure - the vicious cycles that lead to these commandments being broken - and in the climax we have "the way of grace" or "the way of the Kingdom".
These five sayings should be read as threefold teachings, as follows:
(1) The commandment: You have heard that it was said to the people long ago, 'Do not murder, and anyone who murders will be subject to judgment.'
(2) The cause of failure: But I tell you that anyone who is angry with his brother will be subject to judgment. Again, anyone who says to his brother, 'Raca,' is answerable to the Sanhedrin. But anyone who says, 'You fool!' will be in danger of the fire of hell.
(3) The way of grace: So, if you are offering your gift at the altar and there remember that your brother has something against you, leave your gift there in front of the altar. First go and be reconciled to your brother; then come and offer your gift. "Settle matters quickly with your adversary who is taking you to court. Do it while you are still with him on the way, or he may hand you over to the judge, and the judge may hand you over to the officer, and you may be thrown into prison. I tell you the truth, you will not get out until you have paid the last penny.
(1) The commandment: You have heard that it was said, 'Do not commit adultery.'
(2) The cause of failure: But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.
(3) The way of grace: So, if your right eye causes you to sin, gouge it out and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell. And if your right hand causes you to sin, cut it off and throw it away. It is better for you to lose one part of your body than for your whole body to go into hell.
(The saying about divorce is in the dyadic form, and is connected to the saying about adultery. They share the same "way of grace" imperative).
(1) The commandment: You have heard that it was said the people long ago, 'Do not break your oath, but keep the oaths you have made to the Lord.'
(2) The cause of failure: But I tell you, Do not swear at all: either by heaven, for it is God's throne; or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. And do not swear by your head, for you cannot make even one hair white or black.
(3) The way of grace: So, simply let your 'Yes' be 'Yes,' and your 'No,' 'No'; anything beyond this comes from the evil one.
(1) The commandment: You have heard that it was said, 'Eye for eye, and tooth for tooth.'
(2) The cause of failure: But I tell you, do not retaliate revengefully by evil means.
(3) The way of grace: So, if someone strikes you on the right cheek, turn to him the other also. And if someone wants to sue you and take your tunic, let him have your cloak as well. If someone forces you to go one mile, go with him two miles. Give to the one who asks you, and do not turn away from the one who wants to borrow from you.
(1) The commandment: You have heard that it was said, 'Love your neighbor and hate your enemy.'
(2) The cause of failure: If you love those who love you, what reward will you get? Are not even the tax collectors doing that? And if you greet only your brothers, what are you doing more than others? Do not even pagans do that? Be perfect, therefore, as your heavenly Father is perfect.
(3) The way of grace: But I tell you: Love your enemies and pray for those who persecute you, that you may be sons of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.
To be continued.