Jesus gives us the answer in Matthew 18:15: “When your brother sins go and show him his fault in private.” The answer, then, to when to confront sin in a Christian is “when your brother sins.”
But what sins do I confront in a fellow Christian? Do I confront some sins? All sins? Egregious sins? Ten Commandment-kind-of-sins? Let me gives three guidelines for what sins you should confront.
1. Public sins
Open not closed; visible not invisible; objective not subjective; action not attitude; outward not inward.
Outward words or behavior always has inward heart motivations (Mark 7:14-23). But you are not Jesus, and you do not know the heart of man completely and fully (cf. John 2:24). Be very careful about confronting heart motivations.
The sin should be “public.” “Public,” in this sense, does not mean the sin must be performed in public (like school, church, or online), for the sin could be committed in the privacy of home. “Public” means you are not confronting heart motivations.
2. Pattern sins
Is the sin a pattern in the person’s life or a one-time occurrence? Bill stubs his toe at church and lets out a curse. Should you confront him? Perhaps. The question is: is cursing a pattern for Bill?
Patterned sins mean it is a practice or habitual pattern of life. Pattern sins are also likely to be unrepentant sins: sins that a person is unwilling to give up.
3. Precise sins
Precise means that the sin is a “sin” as defined by the Scriptures. Do not confront a preference or conscience issue.
For example, can a Christian watch an R-rated movie? Christians can discuss the wisdom and value in watching an R-rated movie, but watching an R-rated movie is not in itself sin. It might be sin for you to watch an R-rated movie, because your parents instructed you not to, or because in doing so you violate your conscience. But the Bible nowhere forbids the watching of an R-rated movie. The Bible does, however, forbid adultery, stealing, and drunkenness—these are precise sins.
Though never fun and always challenging, when should you confront a Christian who sins? Evaluate the offense using these three “p” guidelines (guidelines—not hard and fast rules): is it public, is it a pattern, and is it precisely a Scriptural sin? If it fits all three, then that’s the sin, with the enabling of the Holy Spirit, you should confront.
Having said this, before you confront any sin, make sure you “cast the log out of your eye” (Matthew 7:1-5). Confront with a heart of love and gentleness (Galatians 6:1-2). For Christ corrects you, but He does so in love and gentleness (Matthew 11:29).
For more on biblical confrontation, see the sermon from Pastor Jeff here.