First convince them they are sick

Their grand plea is this: “That preaching the gospel (that is, according to their judgment, the speaking of nothing but the sufferings and merits of Christ) answers all the ends of the law.” But this we utterly deny. It does not answer the very first end of the law, namely, The convincing men of sin, the awakening those who are still asleep on the brink of hell. There may have been here and there an exempt case. One in a thousand may have been awakened by the gospel. But this is no general rule. The ordinary method of God, is to convict sinners by the law, and that only. The gospel is not the means which God has ordained, or which our Lord himself used, for this end. We have no authority in scripture for applying it thus, nor any ground, to think it will prove effectual. Nor have we any more ground to expect this, from the nature of the thing. Those who are whole, as our Lord himself observes, need not a physician, but those who are sick (Matthew 9:12). It is absurd therefore to offer a physician to those who are whole, or that at least imagine themselves so to be. You are first, to convince them, that they are sick. Otherwise they will not thank you for your labor. It is equally absurd to offer Christ to them, whose heart is whole, having never yet been broken. It is in the proper sense, casting pearls before swine (Matthew 7:6). Doubtless, they will trample them under foot. And it is no more than you have reason to expect, if they also turn again and rend you.