In my opinion, one of the best brief discussions about the law/gospel distinction was written by Thomas Boston and it’s found in the second part of his comments on Edward Fisher’s Marrow of Modern Divinity. In this section Boston explains why a law/gospel distinction is necessary, what the difference is between the law and the gospel, and how to properly distinguish between the two. Below is one section that I found very helpful and comforting – and notice how he explains justification by grace alone through faith alone in Christ alone in light of the law/gospel distinction (the emphasis below is mine):
Briefly, then, if we would know when the law speaks, and when the gospel speaks, either in reading the word, or in hearing it preached; and if we would skilfully distinguish the voice of the one from the voice of the other, we must consider,
Law. The law says, “Thou art a sinner, and therefore thou shalt be damned;” Rom. 7:2; 2 Thess. 2:12.
Gos. But the gospel says, No; “Christ Jesus came into the world to save sinners;” and therefore “believe on the Lord Jesus Christ, and thou shalt be saved,” 1 Tim. 1:15; Acts 16:31.
Law. Again the law says, “Knowest thou not that the unrighteous shall not inherit the kingdom of God; be not deceived,” &c. 1 Cor. 6:9. And therefore thou being a sinner, and not righteous, shall not inherit the kingdom of God.
Gos. But the gospel says, “God has made Christ to be sin for thee, who knew no sin; that thou mightest be made the righteousness of God in him, who is the Lord thy righteousness,” Jer. 23:6.
Law. Again the law says, “Pay me that thou owest me, or else I will cast thee into prison,” Matt. 18:28, 30.
Gos. But the gospel says, “Christ gave himself a ransom for thee,” 1 Tim. 2:6; “and so is made redemption unto thee,” 1 Cor. 1:30.
Law. Again the law says, “Thou hast not continued in all that I require of thee, and therefore thou art accursed,” Deut. 27:6.
Gos. But the gospel says, “Christ hath redeemed thee from the curse of the law, being made a curse for thee,” Gal. 3:13.
Law. Again the law says, “Thou art become guilty before God, and therefore shalt not escape the judgment of God,” Rom. 3:29; 2:3.
Gos. But the gospel says, “The Father judgeth no man, but hath committed all judgment to the Son,” John 5:12.
And now, knowing rightly how to distinguish between the law and the gospel, we must, in the fifth place, take heed that we break not the orders between these two in applying the law where the gospel is to be applied, either to ourselves or to others; for albeit the law and gospel, in order of doctrine, are many times to be joined together, yet, in the case of justification, the law must be utterly separated from the gospel.
Therefore, whensoever, or wheresoever, any doubt or question arises of salvation, or our justification before God, there the law and all good works must be utterly excluded and stand apart, that grace may appear free, and that the promise and faith may stand alone: which faith alone, without law or works, brings thee in particular to thy justification and salvation, through the mere promise and free grace of God in Christ; so that I say, in the action and office of justification, both law and works are to be utterly excluded and exempted, as things which have nothing to do in that behalf. The reason is this; for, seeing that all our redemption springs out from the body of the Son of God crucified, then is there nothing that can stand us in stead, but that only wherewith the body of Christ is apprehended.
Covenant Presbyterian Church (OPC)
Hammond, WI, 54015