4 neither filthiness, nor foolish talking, nor coarse jesting, which are not fitting, but rather giving of thanks.
Verse four introduces a new category of sins, the sins of the tongue.
“Filthiness” is shameful talk and behavior. Obscene talk should not be characteristic of Christians. A filthy person is shameless, someone who does not care about what others think of his sin or about how much he sins. He does not care what the public thinks about his spiritual aberrance.
nor foolish talking,
Literally, “foolish talking” is stupid words. There is such a thing as talk of fools. This kind of talk is folly; it is a person who tears down what is noble and praiseworthy. “Foolish talking” is talk, such as frivolous and senseless communication, that characterizes fools.
nor coarse jesting,
“Coarse jesting” is vulgar or frivolous jocularity. The Greek word here is not found elsewhere in the New Testament. A coarse jester speaks without principle. He can speak about anything according to shifting circumstances and moods, turning any conversation into something dirty. “Coarse” joking is vulgar humor.
which are not fitting,
Improper speech is out of place for a believer. It is unseemly to what Christianity is about. That kind of speech is not worthy of the calling of a Christian; it is not appropriate for a believer.
but rather giving of thanks.
Instead of improper speech, a Christian’s speech should be characterized by “thanksgiving.” Rather than venting oneself with vile speech, it is better to orient oneself around God’s blessing. Grace-oriented thinking is how a Christian should communicate.
Speech that tears down others is improper for believers.
A dirty mind expresses itself in a dirty mouth. Foul communication is not appropriate for a believer, for it is pointless. God designed the sex drive to be kept within bounds. If we do not keep it in bounds, then it will eventually lose its attraction and power. The resulting sexual looseness is pointless and vain.