Ephesians 4:29
Do not allow unwholesome [Note: The Greek word for "unwholesome" is "rotten, diseased"] language to come from your mouth, but only what is helpful for building up those who need it, so that you can impart favor [i.e., benefit] to those who listen [to you].
Ephesians 5:4
Nor should obscenity, silly chatter or double-meaning jokes be used, because they are not proper either. But instead, [you should express] thanksgiving.
Colossians 4:4
[Pray] that I will make it [clearly] known, as I ought to.
James 3:2
For we all make mistakes in many areas [of life]. If anyone does not make a mistake in what he says, he is a perfect person, capable of keeping a tight rein on his whole life also.