Don’t Play With Fire! A Warning About Sin in the Life of a Christian
Christians must be very careful about their behavior and never allow themselves to think, “It doesn’t matter what I do, God is going to forgive me no matter what.” No, dear friends. Do not play with fire! Here is how Martin Chemnitz explains it in his “Enchiridion.”
What If We Indulge and Delight in Evil Lusts and Seek Occasions to Give Them Free Rein (Ro 6:12; MI 2:1; Ja 1:15)?
Then they become mortal sins (Ro 8:13; Ja 1:15), because there surely is no room for true repentance and faith where the lusts of the flesh are served and given rein, so that they break out into action. 1 Ti 1:19; 5:8; 2 Ptr 1:9. It is the nature and particular character of true faith that it does not seek how to commit, continue, and heap up sins freely, but rather hungers and thirsts after the righteousness that releases and frees from sins. Therefore, where there is no true repentance, the Holy Spirit pronounces a very solemn sentence. Jer 5:3, 9; Ro 2:5, 9; Lk 13:3; Rv 2:5. And where there is no true faith, there is neither Christ, nor the Holy Spirit, nor the grace of God, nor forgiveness of sins, nor any salvation. Therefore what? Doubtless the wrath of God, death, and eternal condemnation, unless the fallen are turned to God again. Cl 3:6; Ro 8:13. As a result of this, therefore, and for this reason mortal sins occur in the reborn, namely when repentance, faith, Christ, and the Holy Spirit are driven out and lost.
How, Then, Should One Deal with Those Who Have Fallen into This Kind of Sins?
Their sins are not to be disguised by silence, camouflaged, excused, or defended, but solemnly and earnestly censured and rebuked. Is 56:10; 58:1; Eze 13:10, 18; 2 Ti 4:2; Tts 1:13: “Reprove them sharply,” in such a way that the fearful judgment of God is threatened on them; 1 Co 6:10; Gl 5:21; Cl 3:6; 1 Jn 3:15; Mt 11:21; 2 Ptr 2:10. For he that regards those people as true Christians, and charms and misrepresents them, not only miserably misleads them, but also makes himself partaker of their damnation. Is 3:12; Jer 8:11; 23:17; Eze 3:18; 33:8. Now, the preaching of repentance, rebuking sins, is the instrument and means by which God wants to lead fallen sinners back to the way and convert them. Jer 26:2–3. But if the wicked, neglecting this means, will persevere and continue in his wickedness, he indeed shall perish, but the word of the minister shall deliver his soul. Eze 3:19.
But What If the Fallen Rise Again by the Grace of God and Earnestly Repent?
Then they are indeed to be received with joy and are to be restored and supported with the declaration of the forgiveness of sins. Jer 3:12; 18:8; Eze 18:21; 33:15; Mt 18:13, 27; Lk 15:7. This is what the examples of Scripture testify, e.g., Peter, David, the prodigal, the Corinthians and Galatians. And this indeed not only seven times, but seventy times seven times, Mt 18:22.
Martin Chemnitz and Luther Poellot, Ministry, Word, and Sacraments : An Enchiridion, electronic ed., 104-05 (St. Louis: Concordia Publishing House, 1999).


How can I judge if one’s repentance is earnest?
Why do you ask?
It was in reference to the last question: “But What If the Fallen Rise Again by the Grace of God and Earnestly Repent?”
Is it our place to judge what is earnest repentance? I’m thinking of the situations where one repents, yet they also continue to commit the same sin, sometimes putting up more of a struggle than at other times; perhaps appearing to put up no struggle at all in some cases. Is this earnest repentance?
Also, I’m wondering if a pastor must take someone who is repenting at their word, regardless of their past performance of struggling (or non-struggling).
Take, for example, a couple living together out of wedlock. One says he repents because he is convinced it is sin, yet following this, they continue to live together. Must we judge his repentance as dis-earnest, or is it possible that his repentance was earnest at the time, yet he has once again fallen to temptation? Say this pattern continues…must the pastor withhold forgiveness until they have gotten separate living arrangements or, that is, until the pastor judges the repentance is earnest?
The important thing, I guess, is that he needs to know that he is (still) sinning (or: once again sinning), and that he (still) has a Savior if he repents.
I’m just trying to think this through…
How does one respond to people who, judging by all outward appearances, seem to be content to continue to live in gross sin and vice as described above but yet claim to be Christians because they still confess and believe that Jesus is Lord (i.e., God), and believe that He rose from the dead? How can one be in mortal sin and still have faith that Jesus is the Christ, the Son of God, without having life in His name? I have family members in this condition and don’t know what to say to them because I know these promises are true and don’t want to diminish their force, but know also that these family members are misusing the promises as a license to sin. I can tell them that they have driven out Christ, the Holy Spirit and faith but they would say they still have faith, and therefore also Christ and the Holy Spirit.