Prov. 12:14 - From the fruit of his mouth a man is satisfied with good, and the work of a man's hand comes back to him.
Prov. 13:2 - From the fruit of his mouth a man eats what is good, but the desire of the treacherous is for violence.
What's fascinating about the plethora of Proverbs addressing what we speak is that we are never given a list of words that are unacceptable, except as it pertains to profaning the 'name' of the Lord (cf. Prov. 30:9). In fact, nearly all the references to human speech in the Proverbs don't give you a lot of external specifics. It provides you external scenarios of bad and good speech, but the clear focus of the Proverbs is to get you contemplate the underlying motives involved in human speech.
Part of the problem it seems to me is that we approach Proverbs like we would the Mosaic Law, the later of which is replete with very specific instructions of what one should do and not do. Wisdom literature and the Law fit together under the broad umbrella known as the Mosaic Covenant (cf. 'Listen, my son' in Prov. 1:8 seems clearly intended to mirror the shema of Deut. 6), but on a rhetorical level they communicate truth to us differently. That's part of why we designate the Proverbs as 'wisdom' literature -- if you read them expecting specific instructions (a la Leviticus or Deut.), you ironically end up gutting the very approach that Proverbs lays forth as how one might acquire wisdom. To a person who seeks a specific rule for every situation, there really isn't much need to acquire hokma!
Twice here in Proverbs 12 and 13, we find a connection between our mouths and simply what's good. No list -- the only category it gives is tov!
I think this is helpful to keep in mind when thinking about speech, because it helps us realize that we need more than simply a 'list' of 'bad' words to avoid. If you start with an external list, then you easily put the cart before the horse, ethics prior to redemption, the imperative before the indicative.
Proverbs understands the subtlety and complexity that the language of communication involves -- which is why it addresses the tongue/mouth frequently -- and that's part of the real profundity of the Bible's so-called 'wisdom literature'. It's not just imparting moral slogans to follow, but it's providing us with a 'covenantal worldview' to evaluate *all* our speech. This goes well-beyond (while including in its evaluation) certain 'words' that might bring a perverse connotation.
For example, there is a time to answer a fool and a time NOT to answer a fool? (Prov. 26:4-5) How do you know the difference? Proverbs doesn't spell it out for you in 'how to' fashion -- "Here's when you do it; here's when you don't!." You simply don't get that. What it does spell out for you is the goal and need for *Biblical wisdom* in deciding the difference, and then providing numerous metaphors and parallelisms that help flesh that out.
This is crucial in evaluating our speech -- there are times when certain language is appropriate, times when it is not appropriate, times when it virtually never appropriate. But how do you know? When do parents talk to their children about topics like sex and drugs? How do parents talk to their children about course language without actually using the language itself? That's why you need 'wisdom' -- the ability to show skill in thinking through what you say with your lips.
I have a Christian friend who's an ADA, and he often has to read depositions and statements aloud in court that involve foul language. Is that wrong? For some, I think that would be a major conscience issue -- they would NOT want to answer such a fool according to his own folly! And so they should refrain from doing that. But for the prosecutor, he recognizes civil justice requires the confrontation of people's sinfulness -- 'answering a fool according to his own folly'....even if that means having to repeat the fool's language to the courts.
The difficulty is that this sounds (at least on the surface) a lot like situation ethics. But Fletcher's whole approach to situational ethics rules out any need for Biblical wisdom in making decisions -- I simply say what 'feels' right at any given moment. Biblical wisdom is nothing like that at all -- it recognizes that complexity of 'situations'...but then seeks to bring Biblical truth to bear in evaluating the situation. [Think of the old 'one meaning, many applications', if you will.]
In short, Wisdom recognizes the massive difference between dropping an 'f bomb' out of anger....and dropping an 'f bomb' while reading a transcript in the middle of prosecuting a major felon. This is not a totally arbitrary distinction based on autonomous thinking; rather, it is recognizing that 'wisdom' is rooted in our creation-ethics, for it is "he who made the earth by his power, who established the world by his wisdom" (Jer. 10:15).
Stated pejoratively, Biblical wisdom in both Testaments is neither a friend to the Theonomist or autonomist. That's why it's called Biblical wisdom!
That's also why the 'fear of the Lord' is so important when reading the Proverbs (e.g. 1:7)! We often gloss 'fear' in Proverbs with the idea of 'reverence'....which is not wrong per se, but doesn't really go far enough! John Murray gave, I think, a much more probing (and Biblically-satisfying) definition -- "The fear of God is the soul of godliness...The first thought of the godly man in every circumstance is God's relation to him and it, and his and its relationship to God." (Principles of Conduct, 229).
We have to constantly evaluate all our language -- not merely certain 'words' designated as offensive! -- in light of our relationship to God in Christ! And our standard cannot simply be whether 'it is bad'....but rather whether it is truly good!
Is not that message we see Jesus preaching when confronted about the lawfulness of healing on the Sabbath? (Matt. 12:9-14) . How does Jesus confront their Pharisaical thinking? "It is lawful to do good on the Sabbath." The answer sounds almost too simple....and yet it takes real skill when trying to evaluate what is good to do on the Lord's Day. No list could ever hope to accomplish all that is involved there.
Thankfully, Jesus gives us his own standard for evaluating what is good: And because of him you are in Christ Jesus, who became to us wisdom from God, righteousness and sanctification and redemption, so that, as it is written, “Let the one who boasts, boast in the Lord." (I. Cor. 1:30-31). Not merely content to tell us to do good, Christ in the Gospel becomes wisdom for us!