First, Because, if we be ignorant thereof, we shall be very apt to mix and mingle them together, and so to confound the one with the other; which, as Luther on the Galatians, p. 31, truly says, "doth more mischief than man's reason can conceive"; and therefore he doth advise all Christians, in the case of justification, to separate the law and the gospel as far asunder as heaven and earth are separated.
Secondly, Because if we know right how to distinguish betwixt them, the knowledge thereof will afford us no small light towards the true understanding of the Scripture, and will help us to reconcile all such places, both in the Old and New Testament, as seem to be repugnant; yea, and it will help us to judge aright of cases of conscience, and quiet our own conscience in time of trouble and distress; yea, and we shall thereby be enabled to try the truth and falsehood of all doctrines; wherefore, for our better instruction on this point, we are first of all to consider and take notice what the law is, and what the gospel is.
Now, the law is a doctrine partly known by nature, teaching us that there is a God, and what God is, and what he requires us to do, binding all reasonable creatures to perfect obedience, both internal and external, promising the favour of God, and everlasting life to all those who yield perfect obedience thereunto, and denouncing the curse of God and everlasting damnation to all those who are not perfectly correspondent thereunto.
But the gospel is a doctrine revealed from heaven by the Son of God, presently after the fall of mankind into sin and death, and afterwards manifested more clearly and fully to the patriarchs and prophets, to the evangelists and apostles, and by them spread abroad to others; wherein freedom from sin, from the curse of the law, the wrath of God, death, and hell, is freely promised for Christ's sake unto all who truly believe on his name.
Thirdly, We are to consider what the nature and office of the law is, and what the nature and office of the gospel is.
Now, the nature and office of the law is to show unto us our sin, (Rom 3:10), our condemnation, our death, (Rom 2:1, 7:10). But the nature and office of the gospel is to show unto us, that Christ has taken away our sin, (John 1:29), and that he also is our redemption and life, (Col 1:14, 3:4). So that the LAW is a word of wrath, (Rom 4:14); but the GOSPEL is a word of peace, (Eph 2:17).
Fourthly, We are to consider where we may find the law written, and where we may find the gospel written.
Now, we shall find this law and this gospel written and recorded in the writings of the prophets, evangelists, and apostles, namely, in the books called the Old and New Testament, or the Scriptures. For, indeed, the law and the gospel are the chief general heads which comprehend all the doctrine of the Scriptures; yet we are not to think that these two doctrines are to be distinguished by the books and leaves of the Scriptures, but by the diversity of God's Spirit speaking in them: we are not to take and understand whatsoever is contained in the compass of the Old Testament, to be only and merely the word and voice of the law; neither are we to think that whatsoever is contained within the compass of the books called the New Testament, is only and merely the voice of the gospel; for sometimes in the Old Testament, God does speak comfort, as he comforted Adam, with the voice of the gospel; sometimes also in the New Testament he does threaten and terrify, as when Christ terrified the Pharisees. In some places, again, Moses and the prophets do play the evangelists; insomuch that Hierom doubts whether he should call Isaiah a prophet or an evangelist. In some places, likewise, Christ and the apostles supply the part of Moses: Christ himself, until his death, was under the law, which law he came not to break, but to fulfil; so his sermons made to the Jews, for the most part, run all upon the perfect doctrine and works of the law, showing and teaching what we ought to do by the right law of justice, and what danger ensues in the non-performance of the same. All which places, though they be contained in the book of the New Testament, yet are they to be referred to the doctrine of the law, ever having included in them a privy exception of repentance and faith in Jesus Christ. As for example, where Christ thus preaches, "Blessed are the pure in heart, for they shall see God," (Matt 5:8). Again, "Except ye be converted and become as little children, ye shall not enter into the kingdom of heaven," (Matt 18:3). And again, "He that doeth the will of my Father which is in heaven, shall enter into the kingdom of heaven," (Matt 7:21). And again, the parable of the wicked servant, cast into prison for not forgiving his fellow, (Matt 18:30); the casting of the rich glutton into hell, (Luke 16:23). And again, "He that denieth me before men, I will deny him before my Father which is in heaven," (Luke 12:9); with divers such other places, all which, I say, do appertain to the doctrine of the law.
Wherefore, in the fifth place, we are to take heed, when we read the Scriptures, we do not take the gospel for the law, nor the law for the gospel, but labour to discern and distinguish the voice of the one from the voice of the other; and if we would know when the law speaks, and when the gospel speaks, let us consider and take this for a note, that when in Scripture there is any moral work commanded to be done, either for eschewing of punishment, or upon promise of any reward, temporal or eternal—or else when any promise is made with the condition of any work to be done, which is commanded in the law—there is to be understood the voice of the law.
Contrariwise, where the promise of life and salvation is offered unto us freely, without any condition of any law, either natural, ceremonial, or moral, or any work done by us, all those places, whether we read them in the Old Testament, or in the New, are to be referred to the voice and doctrine of the gospel; yea, and all those promises of Christ coming in the flesh, which we read in the Old Testament; yea, and all those promises in the New Testament, which offer Christ upon condition of our believing on his name, are properly called the voice of the gospel, because they have no condition of our mortifying annexed unto them, but only faith to apprehend and receive Jesus Christ; as it is written, (Rom 3:22), "For the righteousness of God, which is by faith of Jesus Christ unto all, and upon all that believe," &c.
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 skillfully 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, shalt 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 what 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 are become guilty before God, and therefore shalt not escape the judgment of God," (Rom 3:19, 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 sixth 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. Now, forasmuch as neither the law nor works, but faith only, is the thing which apprehendeth the body and passion of Christ, therefore faith only is that matter which justifies a man before God, through the strength of that object Jesus Christ, which it apprehends; like as the brazen serpent was the object only of the Israelites' looking, and not of their hands' working; by the strength of which object, through the promise of God, immediately proceeded health to the beholders: so the body of Christ being the object of our faith, strikes righteousness to our souls, not through working, but through believing.
Wherefore, when any person or persons, do feel themselves oppressed or terrified with the burden of their sins, and feel themselves with the majesty of the law and judgment of God terrified and oppressed, outweighed and thrown down into utter discomfort, almost to the pit of hell, as happens sometimes to God's own dear servants, who have soft and timorous consciences; when such souls, I say, do read or hear any such place of Scripture which appertains to the law, let them, then, think and assure themselves that such places do not appertain or belong to them; nay, let not such only who are thus deeply humbled and terrified do this, but also let every one that does but make any doubt or question of their own salvation, through the sight and sense of their sin, do the like.
And to this end and purpose, let them consider and mark well the end why the law was given, which was not to bring us to salvation, nor to make us good, and so to procure God's love and favour towards us: but rather to declare and convict our wickedness, and make us feel the danger thereof; to this end and purpose, that we seeing our condemnation, and being in ourselves confounded, may be driven thereby to have our refuge in the Son of God, in whom alone is to be found our remedy. And when this is wrought in us, then the law has accomplished its end in us; and therefore it is now to give place unto Jesus Christ, who, as the apostle says, "is the end of the law," (Rom 10:3). Let every true convicted person, then, who fears the wrath of God, death, and hell, when they hear or read any such places of Scripture as do appertain to the law, not think the same to belong to them, no more than a mourning weed belongs to a marriage feast; and therefore, removing utterly out of their minds all cogitations of the law, all fear of judgment and condemnation, let them only set before their eyes the gospel, viz: the glad and joyful tidings of Christ, the sweet comforts of God's promises, free forgiveness of sins in Christ, grace, redemption, liberty, psalms, thanks, singing, a paradise of spiritual jocundity, and nothing else; thinking thus within themselves, the law hath now done its office in me, and therefore must now give place to its better; that is, it must needs give place to Jesus Christ, the Son of God, who is my Lord and Master, the fulfiller and accomplisher of the law.
Lastly, As we must take heed and beware that we apply not the law where the gospel is to be applied, so must we also take heed and beware that we apply not the gospel where the law is to be applied. Let us not apply the gospel instead of the law; for, as before, the other was even as much as to put on a mourning-gown at a marriage feast, so this is but even the casting of pearls before swine, wherein is great abuse amongst many; for commonly it is seen, that these proud, self-conceited, and unhumbled persons, these worldly epicures and secure mammonists, to whom the doctrine of the law does properly appertain, do yet notwithstanding put it away from them, and bless themselves with the sweet promises of the gospel, saying, "They hope they have as good a share in Christ as the best of them all, for God is merciful and the like." And contrariwise, the other contrite and bruised hearts, to whom belongs not the law, but the joyful tidings of the gospel, for the most part receive and apply to themselves the terrible voice and sentence of the law. Whereby it comes to pass, that many do rejoice when they should mourn; and on the other side, many do fear and mourn when they should rejoice. Wherefore, to conclude, in private use of life, let every person discreetly discern between the law and the gospel, and apply to himself that which belongs to him. Let the man or the woman, who did never yet to any purpose [especially in the time of health and prosperity] think of, or consider their latter end, that did never yet fear the wrath of God, nor death, nor devil, nor hell, but have lived, and do still live a jocund and merry life; let them apply the curse of the law to themselves, for to them it belongs: yea, and let all your civil honest men and women, who, it may be, do sometimes think of their latter end, and have had some kind of fear of the wrath of God, death, and hell, in their hearts, and yet have salved up the sore, with a plaster made of their own civil righteousness, with a salve compounded of their outward conformity to the duties contained in the law, their freedom from gross sins, and their upright and just dealing with men; let these hearken to the voice of the law, when it says, "Cursed is every one that continueth not in all things which are written in the book of the law to do them"; but let all self-denying, fearful, trembling souls, apply the gracious and sweet promises of God in Christ unto themselves, and rejoice because their names are written in the Book of Life.