Mortal Sin

by Nathaniel Biebert

1 Corinthians 10:12. So, if you think you are standing firm, be careful that you don’t fall!

As Lutherans, we often put all of our attention on the Gospel, without looking at the Law and how serious God looks upon sin. The very fact that he sent his own Son to earth to make satisfaction for our sins should be enough to make us tremble at the thought of sin.1 But our puny, rational minds cannot fully comprehend the magnitude and abomination of our sins in the sight of God, nor do they want to, and rightly so. For if we could fully perceive how justly angry the holy God becomes over just one little sin, we would die. Yet, how often we go about our day-to-day lives care-free without giving a thought to the appalling consequences of what we have done! Sometimes Christians give so little thought to sin that they stop worrying about it altogether. These eventually fall into unbelief, because they regard sin so little that they have no need for a Savior from sin. The following essay is an exhortation to “be careful!” Even though we “are not under law, but under grace” (Ro. 6:14), God still takes sin seriously, and we have the dangerous capacity to reject his perfect solution for cleansing from sin.

Venial sin in the regenerate, that is, in Christ’s believers, has already been discussed. But we know that there are cases where sin is not remitted. John records the words of Christ in his Gospel: “If you forgive anyone his sins, they are forgiven; if you do not forgive them, they are not forgiven” (Jn. 20:23). Jeremiah urges the Israelites to confess, “We have sinned and rebelled and you have not forgiven” (Lam. 3:42). Psalm 32:1 states: “Blessed is he whose transgressions are forgiven, whose sins are covered.” This passage, in stating the positive, implies that there is a negative, that is, there are some whose sins are not covered. Talk of hell in Scripture would also be empty and useless if unforgiven sin did not exist. The term that, although not expressly stated in Scripture, helpfully and accurately describes sin that falls under this category is mortal sin.

Speaking of the difference between mortal, or deadly, and venial sin is useless in reference to the unregenerate. Every sin in and of itself, according to God’s perfect Law and outside of Christ, is mortal. For, as Paul says, “everything that does not come from faith is sin” (Ro. 14:23), and “the wages of sin is death” (Ro. 6:23). Thus, the whole life of an unbeliever is one steeped in mortal sin and ultimately results in eternal damnation, because due to their complete lack of faith they have no pardon connected with their sin.

However, we know that this frightful situation is not the case with us. “There is now no condemnation for those who are in Christ Jesus” (Ro. 8:1). Yet Paul warns us in the passage listed above to be careful lest we fall. How do we fall? A fall away from righteousness obviously leads to a state of unrighteousness, which merits death. In order to fall away from righteousness then, one needs to commit deadly, or mortal, sin. Paul is warning us about precisely this.

Therefore do not let sin reign in your mortal body so that you obey its evil desires. Do not offer the parts of your body to sin, as instruments of wickedness, but rather offer yourselves to God, as those who have been brought from death to life; and offer the parts of your body to him as instruments of righteousness. For sin shall not be your master, because you are not under law, but under grace (Ro. 6:12-14).

Here Paul shows us what faith does. Faith is not merely some passive agent. Faith is truly active. By the Holy Spirit’s power it takes hold of God’s promises and says, “These promises are mine! I shall give God thanks and praise through all that I say, think, and do.” The Gospel energizes the new man in us. No, it does more than that-it empowers the new man to rule over the old. Sin is no longer our master; it no longer reigns or has dominion in our bodies! We are willing slaves for God! The Smalcald Articles correctly state:

The Holy Spirit does not permit sin to rule and gain the upper hand in such a way that sin is committed, but the Holy Spirit represses and restrains it so that it does not do what it wishes.2

Granted, we still retain sin, and it taints even the good that we do, as both Isaiah and John testify: “All our righteous acts are like filthy rags” (Isa. 64:6); “If we claim to be without sin, we deceive ourselves and the truth is not in us” (1Jn. 1:8). Nevertheless, sin will not be our master if we have been brought by God from death to life. And our new man will get stronger and stronger as our faith is fed and nourished by the Gospel. Therefore, Luther’s Small Catechism correctly teaches:

[Baptizing with water] signifies that the old Adam in us, together with all sins and evil lusts, should be drowned by daily sorrow and repentance and be put to death, and that the new man should come forth daily and rise up, cleansed and righteous, to live forever in God’s presence.3

John seems to have a double tongue though: “No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him” (1Jn. 3:6). Literally, this passage is laid out very simply: “Everyone who abides in him does not sin. Everyone who sins has not seen him nor has known him.” If this passage is compared to 1 John 1:8 as it is recorded in the previous paragraph, there seems to be a discrepancy. But we know that the Bible does not contradict itself. So what is the Holy Spirit telling us through John? Martin Chemnitz, whose abbreviated biography appeared in the last issue, explains: “In ch. 1 he is speaking of those who have been washed in the blood of Christ, but still have sin in them. But in ch. 3 he is speaking of premeditated sins which thus are a different kind of sin … Thus John is demonstrating that there is a difference between having sin and committing sin4 (emphasis added). The whole Bible does not imitate John in making this distinction across the board, but it is nevertheless a common distinction. In a broad sense, committing a sin refers to what we do every time we act contrary to the Law of God. In a narrow sense, as John uses it here, it refers to what we do when against conscience our “will gives in to depraved lusts and turns itself away from God knowingly, and willingly is contrary to the commandment of God.”5 This is the first half of the definition of mortal sin.

Paul mentions the second half of the definition in Romans 2:4-5:

Or do you show contempt for the riches of his kindness, tolerance and patience, not realizing that God's kindness leads you toward repentance? But because of your stubbornness and your unrepentant heart, you are storing up wrath against yourself for the day of God's wrath, when his righteous judgment will be revealed.

As was recorded earlier in Luther’s explanation of Baptism, faith also produces fruit in keeping with repentance (Mt. 3:8). Christians are fully aware of their sin, and so in response to the Gospel their lives are a battle against it. They daily struggle to “hold on to the good [and to] avoid every kind of evil” (1Th. 5:21b,22). If repentance ceases, then faith is no longer there. This then is the second half of the definition of mortal sin: “[Our will] refuses to repent, to fear God, and to believe Him, which is pleasing to God.”6

To sum it up then, mortal sins are those “which force the Holy Spirit to depart from one’s heart, which destroy faith”7 and ultimately lead to eternal damnation.

One might ask, “Are there certain sins that are automatically mortal sins?” While certain people enumerate seven sins (listed in the article on Venial Sin) as automatically deadly, this is not what Scripture teaches. Potentially mortal sins are listed in Galatians:

The acts of the sinful nature are obvious: sexual immorality, impurity and debauchery; idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this [literally: those who do the things of such kind] will not inherit the kingdom of God (Gal. 5:19-21).

Let’s not kid ourselves--all of these sins are on our record. Even if everything but idolatry were omitted, we would still stand guilty, since every sin, great or small, shows a lack of love for God, and thus breaks the First Commandment which tells us to fear, love, and trust in God above all things. But for the regenerate all of these sins are venial. Why? The key word in this selection is do. It is used in the same way as John uses the verb sin in 1 John 3:6. It denotes a knowing and willing turn away from God towards evil. This does not only have to be a sin of commission. “Woe to me if I do not preach the Gospel” (1Co. 9:16), Paul says. In the parable of the talents, Christ describes the sentence of the servant who did nothing with his talent: “Throw that worthless servant outside, into the darkness, where there will be weeping and gnashing of teeth” (Mt. 25:30). So sins of omission are also included. Therefore, if any sin is committed with an attitude in the heart that rejects the Spirit of God, it is a mortal sin.

The following passages are further testimonies to the seriousness and result of mortal sin:

  • If a righteous man turns from his righteousness and does evil, he will die for it (Eze. 33:18).
  • Then I will tell them plainly, “I never knew you. Away from me, you evildoers!” (Mt. 7:23).
  • But unless you repent, you too will all perish (Lk. 13:3).
  • Do you not know that the wicked will not inherit the kingdom of God? (1Co. 6:9).
  • For if you live according to the sinful nature, you will die (Ro. 8:13).
  • If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, but only a fearful expectation of judgment and of raging fire that will consume the enemies of God (Heb. 10:26,27).

Mortal sin can be a very frightening doctrine. Many, after examining it, approach despair as they wonder if they have committed mortal sin. Or they worry about committing mortal sin in the future, perhaps at the exact time when their time of grace ends in death. They occupy themselves with thoughts such as, “What if I am deliberately speeding, and then I get into a crash and die?” These are indeed frightening thoughts.

The doctrine of mortal sin is not meant to answer the scholastic questions of wandering minds. It is a warning, showing us that God takes sin seriously, and as such it serves as an exhortation for us to avoid neglecting the Gospel. For when faith is fed and nourished by the Gospel in Word and Sacrament, then it cannot help but produce fruits of repentance. If one is diligent in the study of and growth in God’s Word, which is “the power of God for the salvation of everyone who believes” (Ro. 1:16), then sin will not rule in our bodies. Instead, “he who began a good work in you will carry it on to completion until the day of Christ Jesus” (Php. 1:6). So instead of worrying about dying while speeding, we out of love for Christ, who established the government with all its laws, will simply not speed. Instead of worrying about dying while underage drinking or drinking in excess, we out of love for Christ will avoid doing these things to the best of our God-given ability. “Live by the Spirit, and you will not gratify the desires of the sinful nature” (Gal. 5:16). Luther offers the following exhortation and comfort:

Let every man, then, so practise with himself, that his conscience may be fully assured that he is under grace, and that his person and his works do please God. And if he feel any wavering or doubting, let him exercise his faith, and wrestle against it, and labour to attain more strength and assurance of faith, so that he may be able to say, I know that I am accepted, and that I have the Holy Ghost: not for mine own worthiness, work, or merit, but for Christ’s sake, who of His love towards us made Himself subject to the law, and took away the sins of the world. In Him do I believe. If I am a sinner, and err, He is righteous and cannot err. Moreover, I gladly hear, read, write, and sing of Him, and desire nothing more than that His gospel may be known to the whole world, and that many may be converted to Him. These things do plainly witness that the Holy Ghost is present with us and in us.8

This doctrine also serves to make us appreciate all the more the bottomless well of God’s love. Who knows how often we have sinned? And still God whispers to us, “The Lord longs to be gracious to you; he rises to show you compassion” (Isa. 30:18). If some find that they are ignoring their conscience, let them confess and turn from their ignorance, that they may certainly be forgiven. If some are living in mortal sin, they need to hear how dangerous their condition is, and also the Lord’s earnest plea for them to turn from their evil ways and live (Eze. 33:11). For our loving Lord lives to grant life to all who call on him.

The writer of this essay would also like to include an excerpt from C. F. W. Walther’s most excellent book The Proper Distinction Between Law and Gospel. The lectures contained in this book are directed at future ministers of the Gospel. He touches on the subject of mortal sin on page 55:

Another point that you will have to bear in mind while writing your sermons [preparing your lessons, etc.] is not to say anything that may be misunderstood. For instance, this statement is liable to misconstruction: “Any one sinning purposely and knowingly falls from grace.” For true Christians occasionally sin with intent and knowledge, namely, when they are, so to speak, rushed by a sinful passion from within or by allurements from without. Such sins are called hasty sins. Here is one with a wrathful temper, though, as a rule, amiable. Something crosses his path, and suddenly he boils over in angry speech. In such a case the Spirit of God will administer to the culprit this rebuke: “Behold, what a miserable creature thou art!” and prompt him to ask God’s forgiveness. It is true, indeed, that a Christian sinning intentionally grieves the Spirit of God every time. The Holy Spirit will not take part in his action. Regarding this matter we must therefore speak to people in this manner: “You are treading on dangerous ground. The Holy Spirit will withdraw from you, and instead of making progress in your Christianity, you will be thrown back. If you do not repent and remain genuinely penitent, this sin may be your ruin."

In closing, the writer would like to point out that one of the most common examples used by our Lutheran fathers of the regenerate committing mortal sin is the example of David. David deliberately went against God’s written Law and his own conscience when he committed adultery with Bathsheba. He then proceeded to steep himself further in his sin by committing other atrocious sins (2Sa. 11). Most importantly, David failed to repent of his sin. Yet the Lord, who longs to be gracious, sent his prophet to David to confront him about his sin and to crush him with the Law in order to make David realize and confess his sin. When David simply confessed, “I have sinned against the Lord,” the Lord’s prophet did not respond with, “You sure did!” Rather, the prophet’s immediate comforting message to David was, “The Lord has taken away your sin. You are not going to die” (2Sa. 12:1-13). The Lord forgave David, who had been on the path to hell, and used him to write many beautiful Psalms, which are full of comfort for the oppressed and heavy-laden sinner.

Please refer to Martin Chemnitz’s Loci Theologici, cited in the footnotes for this essay, for an extremely thorough treatment of mortal and venial sin. Chapter V: The Use of This Doctrine, found on pages 680-681, is especially well written and useful.

  • 1. Note well: This is not the primary use of the Gospel, but is known as the “strange work” of the Gospel. The Gospel should ultimately serve to comfort us.
  • 2. Tappert, 310.
  • 3. Tappert, Theodore G., ed. The Book of Concord: The Confessions of the Evangelical Lutheran Church. Philadelphia, PN: Fortress Press, 1959. Pg. 349.
  • 4. Chemnitz, Martin. Loci Theologici: Vol. II. St. Louis, MO: Concordia Publishing House, 1989. Pg. 672.
  • 5. Ibid., 668. (Chemnitz is here quoting from Philip Melancthon’s text in Loci Communes.)
  • 6. Chemnitz, 668. (Chemnitz is again quoting Melancthon.)
  • 7. Pieper, Francis. Christian Dogmatics: Volume I. St. Louis, MO: Concordia Publishing House, 1950. Pg. 568.
  • 8. Luther, Martin. Commentary on Galatians. Grand Rapids, MI: Kregel Classics, 1979. Pg. 243.