3 But fornication and all uncleanness or covetousness, let it not even be named among you, as is fitting for saints;
The vices listed in verses three and four are the opposite of the virtues of verses one and two. There is a shift from the example of Christ’s sacrificial giving to extreme examples of selfishness.
The “but” here shows contrast to 4:25-5:2. The previous section concerned itself with conduct Christians should adopt. Now the Holy Spirit speaks to things believers should avoid (5:3-14). The previous section dealt with sins against others, but this section deals with sins against ourselves.
“Fornication” is any kind of sexual sin. It is far more than sex between single people who are not married.
and all uncleanness
“Uncleanness” is impurity. Impurity is anything thing that is sexually filthy. This word occurs 10 times. All but one time (Mt 23:27) “uncleanness” refers to sexual sin. This can carry ideas such as sexual perversion and immoral passion, thoughts, or fantasies.
“Covetousness” is greed or the desire to have more. Sexual sins are often connected to greed. The idea is self-gratification sexually. Love gives but greed takes. Greed is the motivation for all sins.
let it not even be named among you,
The previous sins were not to be named among the saints. It does not say “practiced.” The sins of this verse should never be mentioned among the saints. Transformed people should act like converted saints. Saints should not in any sense speak with approval about these things.
as is fitting [proper] for saints;
The three sins of this verse are fitting for sinners but not for saints. The sins of this verse are contrary to what it means to be a Christian. Sins of sensuality are completely inconsistent with the character of being a believer.
Sexual sins cannot be justified or tolerated among the saints.
The purpose of sexual sins is to get, not to give. It is the desire to exploit others for selfish ends. A concept that we are not to allow to be once named is now pervasive in western Christian culture. Pornography is rampant among Christian men today. The core problem behind this sin is not pornography itself but the belief in what ultimately fulfills the individual. The desire for explicit imagery is an idolatry that inserts itself in the place of God. It is the attempt to displace what only God can fill.
The problem with sexual sin is that it is incompatible with Christianity because it debases and defiles humanity. That is, Christians are not even to “name” these sins among themselves. It is important to note that this is not a prohibition against discussing sex, but it is a prohibition against portraying or speaking of aberrations of sex as normal.