John Wesley is one of the great interpreters of Jesus’ Sermon on the Mount. The Sermon plays a central role in Wesley’s own thought. In Wesley’s Standard Sermons, the series of sermons dedicated to expounding Jesus’ Sermon on the Mount is the longest series of continuous discourses in the whole volume, running from Sermon #21 to #33.
The reason Wesley gave such a large percentage of his book to these three chapters of Matthew is that he wanted to provide an extended example of the searching, penetrating preaching of the law that he believed should characterize Christian preaching. He fixes on the Sermon on the Mount as the best text for expounding the law, because though the law was classically presented in the Old Testament, it was explained more fully by Christ himself. The law was “never so fully explained, nor so thoroughly understood, till the great author of it himself condescended to give mankind the authentic comment on all the essential branches of it; at the same time declaring it should never be changed, but remain in force to the end of the world.”
So expounding the “Our Lord’s Sermon on the Mount” (the title of the sermon series) gave Wesley the opportunity to present the central meaning of the law by expounding the words of Christ. It is a way of reaffirming the Old Testament on the ground of the New Testament; maintaining the connection with God’s intent in the law, but acknowledging that the gospel has come in the meantime.
There are Protestant precedents for this kind of move. The Heidelberg Catechism, for example, does something like this when it introduces the law with the question, “What does the law of God require of us?” (question 4) and then goes directly to the words of Jesus for its initial answer:
Christ teaches us that briefly, Matt. 22:37-40, ‘Thou shalt love the Lord thy God with all thy heart, with all thy soul, and with all thy mind, and with all thy strength. This is the first and the great commandment; and the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and the prophets.’
It is a consummately Christian maneuver to receive the Old Testament law from Jesus, and the nomophilic Heidelberg Catechism sends an important signal with this early move. But the Heidelberg Catechism postpones its full treatment of the law until much later (question 91 and following), when it poses the question “What is the law of God?” and then answers with the Ten Commandments, which it then proceeds to work through, one at a time. The Ten Commandments, in fact, are a set piece within any Protestant catechism; you can’t have a decent catechism without exposition of the Ten Commandments. The Heidelberg Catechism therefore signals the fact that it intends to teach the law in a Christian manner (“Christ teaches us that briefly”) before setting in to expounding the words of the Old Testament.
But Wesley, preaching rather than catechizing, has more space and more options. He takes advantage of this freedom to frame his entire exposition of the law as a commentary on the words of Christ. Wesley confronts his hearers (or readers) with the whole law of God, at some length, in the words and from the mouth of Jesus Christ.
Wesley has an ingenious outline of the Sermon the Mount. He calls the large, middle section (from 5:17 to 7:12) “a description of true Christian holiness,” noting that Jesus proceeds through this section with a series of “you have heard… but I say” contrasts. In each of these contrasts, Jesus focuses on some aspect of the law of God, intensifying it and applying it to the heart of the hearer. That is the main point of the sermon, according to Wesley: true holiness in Christ, distinguished from merely external religion. The beatitudes (5:3-12) he calls “a sweet invitation to true holiness and happiness, and the sayings about Christ’s followers being salt and light (5:13-16) he calls “a persuasive to impart” that true holiness and happiness “to others.” Christ concludes the Sermon (7:13-27) with a series of stark alternatives (the two paths, the two trees, and the two foundations), which Wesley says provide “a sure mark of the true way.”
The key text in the Sermon on the Mount, then, is Jesus’ statement in 5:17 that he came “not to destroy the law and the prophets, but to fulfill them.” True Christian holiness is placed in contrast to mere outward religion, but never in contrast to God’s law.