As I was preparing to preach last Sunday, I read through Wesley's Sermon 25: Sermon on the Mount, V, once again. I found it to be very relevant for my preaching from that section of Jesus' Sermon on the Mount. The following quotes come from Wesley's sermon:
From all this we may learn that there is no contrariety at all between the law and the gospel; that there is no need for the law to pass away in order to the establishing of the gospel. Indeed neither of them supersedes the other, but they agree perfectly well together. Yea, the very same words, considered in different respects, are parts both of the law and of the gospel. If they are considered as commandments, they are parts of the law; if as promises, of the gospel. Thus, 'Thou shalt love the Lord thy God with all thy heart,' when considered as a commandment, is a branch of the law; when regarded as a promise, is an essential part of the gospel - the gospel being no other than the commands of the law proposed by way of promises. Accordingly poverty of spirit, purity of heart, and whatever else enjoined in the holy law of God, are no other, when viewed in a gospel light, than so many great and precious promises.
There is therefore the closest connection that can be conceived between the law and the gospel. On the one hand the law continually makes way for and points us to the gospel; on the other the gospel continually leads us to a more exact fulfilling of the law. The law, for instance, requires us to love God, to love our neighbour, to be meek, humble, or holy. We feel that we are not sufficient for these things, yea, that 'with man this is impossible.' But we see a promise of God to give us that love, and to make us humble, meek, and holy. We lay hold of this gospel, of these glad tidings: it is done unto us according to our faith, and 'the righteousness of the law is fulfilled in us' through faith which is in Christ Jesus.
We may yet farther observe that every command in Holy Writ is only a covered promise. For by that solemn declaration, 'This is the covenant I will make after those days, saith the Lord; I will put my laws in your minds, and write them in your hearts,' God hath engaged to give whatsoever he commands.
Later, in the same sermon, Wesley says:
. . . And we must all declare, 'By grace ye are saved through faith: . . . not of works, lest any man should boast.' We must cry aloud to every penitent sinner, 'Believe in the Lord Jesus Christ, and thou shalt be saved.' But at the same time we must take care to let all men know we esteem no faith but that 'which worketh by love'; and that we are not 'saved by faith' unless so far as we are delivered from the power as well as the guilt of sin. And when we say, 'Believe, and thou shalt be saved,' we do not mean, 'Believe, and thou shalt step from sin to heaven, without any holiness coming between, faith supplying the place of holiness;' but, believe and thou shalt be holy; believe in the Lord Jesus, and thou shalt have peace and power together. Thou shalt have power from him in whom thou believest to trample sin under thy feet; power to love the Lord thy God with all thy heart, and to serve him with all thy strength.