When it comes to the Sermon on the Mount, even readers of The Abolition of Man by C.S. Lewis seem blissfully unaware of his premise, that our Lord did not bring any new teaching on morality, or any novel approach to ethics. Furthermore, this seems even more true concerning the second half of that premise: that had the Lord introduced startling new concepts of morality never before known, we should suspect him of fraud and doubt his goodness. How then do we read the Sermon on the Mount, especially those parts in which we have heard from those of old time, and then we hear the words, “But I say unto you…” as if he was presenting an original thought with an air of authority? Lewis presented the anthropological and historical evidence that demonstrates universal knowledge of morality and ethics among all of the various ancient nations, even amidst their paganism. And, though the light in them was, by the Divine standard, darkness, it was light enough to make them aware of right and wrong (Romans 1: 19, 20). How much more was the understanding of a people true light indeed, as that light shone among the Jews, whose morality came from the Law revealed by God to his servant Moses.
We have been conditioned to think that, in the Sermon on the Mount, Jesus was presenting new insights into morality hitherto unknown by Israel. But, the Lord was teaching the true meaning of the Law, a revelation that had become ancient even by that time. All of his authoritative teaching about right and wrong, and the application of the commandments of God to the deepest and most hidden places of the heart, were clearly evident in the Old Testament scriptures. There was nothing new in his moral teaching.
What was new, however, was the teaching he presented in that sermon on the subject of himself. The startling new doctrine in the Sermon on the Mount was his claim to divinity, a unique relationship to the Father by which he claimed equality with God; the claim that another Gospel, According to John, declares to be the direct cause of his trial and death.
But, in his rabbinical teaching on morality, he commented on the Torah. Compare his words, from these examples, with what we find in the Old Testament.
“Ye have heard that it was said by them of old time, Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment: But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire. Therefore if thou bring thy gift to the altar, and there rememberest that thy brother hath ought against thee; Leave there thy gift before the altar, and go thy way; first be reconciled to thy brother, and then come and offer thy gift.”
“Thou shalt not hate thy brother in thine heart: thou shalt in any wise rebuke thy neighbour, and not suffer sin upon him. Thou shalt not avenge, nor bear any grudge against the children of thy people, but thou shalt love thy neighbour as thyself: I am the LORD.”
Leviticus. 19:17, 18
“For if ye forgive men their trespasses, your heavenly Father will also forgive you:
But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.”
Matthew. 6:14, 15
“He that revengeth shall find vengeance from the Lord, and he will surely keep his sins [in remembrance.] Forgive thy neighbour the hurt that he hath done unto thee, so shall thy sins also be forgiven when thou prayest. One man beareth hatred against another, and doth he seek pardon from the Lord? He sheweth no mercy to a man, which is like himself: and doth he ask forgiveness of his own sins? If he that is but flesh nourish hatred, who will intreat for pardon of his sins? Remember thy end, and let enmity cease; [remember] corruption and death, and abide in the commandments. Remember the commandments, and bear no malice to thy neighbour: [remember] the covenant of the Highest, and wink at ignorance.”
Ecclesiasticus (or Sirach) 28:1-7
“Ye have heard that it was said by them of old time, Thou shalt not commit adultery:
But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart.”
Matthew. 5: 27, 28
“…thou shalt not covet thy neighbour's wife…”
Exodus 20: 17
“I made a covenant with mine eyes; why then should I think upon a maid?”
(Indeed, the understanding of ancient Jews was that such lust and covetousness directed at an unmarried woman was to covet one destined to become another man’s wife.)
In these teachings the Lord was clarifying the meaning of the Law that must be engraved by the Holy Spirit on the human heart as one of the benefits of the New Covenant (Jer. 31: 31-34). The words of David ring loud: “Behold, thou desirest truth in the inward parts: and in the hidden part thou shalt make me to know wisdom… Create in me a clean heart, O God; and renew a right spirit within me.” (Psalm 51: 6, 10) By making this teaching plain and clear on the mountain, he demonstrated that he was the Prophet like unto Moses that would speak with unique authority (Deut. 18: 15), and that the New Covenant would be established through him.
In the Sermon on the Mount, the new and startling doctrine was his own claim to divinity. He does not say “thus saith the Lord,” but rather, “I say unto you.” After this, he goes as far as to begin his teachings with the familiar phrase- familiar to us since he used it so often- “Amen, amen, I say unto you…” No prophet dared to speak this way. And no prophet ever spoke of himself as the One who will exercise the powers of God on the day of judgment. But, our Lord speaks of himself as the One who will judge all men on the last day, as a Man who has the authority of Almighty God:"Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.”
Matthew. 7: 21-23
For this we have no Old Testament parallel, nothing at all to which we can make a comparison. Never a man spoke like this man.
Indeed, new and shocking teaching clearly is found in the Sermon on the Mount; but let’s get it right. This is where we find it: In the Lord's words about himself. The cryptic anti-Semitism that fancies the notion of Jewish ignorance about right and wrong, that subtle thing that colors too much of our thinking, needs to be exorcised from the Christian’s mind forever. What the Lord said that day was new and shocking (just as it was new and shocking on another day when he told them that they must eat of his flesh and drink of his blood to have eternal life). But, it was not his moral teaching that was new and shocking, for the people had been instructed in the Law and the Prophets from childhood. What was new and shocking was his claim to equality with God, this claim from a Man who sat teaching that day on the mount, “pleased as man with man to dwell, Jesus our Emmanuel.”