▼ The contrast is between the “tongue of the wise” and the “mouth of the fool.” Both expressions are metonymies of cause; the subject matter is what they say. How wise people are can be determined from what they say.

▼ Or “makes knowledge acceptable” (so NASB). The verb תֵּיטִיב (tetiv, Hiphil imperfect of יָטַב [yatav, “to be good”]) can be translated “to make good” or “to treat in a good [or, excellent] way” (C. H. Toy, Proverbs [ICC], 303). M. Dahood, however, suggests emending the text to תֵּיטִיף (tetif) which is a cognate of נָטַף (nataf, “drip”), and translates “tongues of the sages drip with knowledge” (Proverbs and Northwest Semitic Philology, 32–33). But this change is gratuitous and unnecessary.

▼ The Hiphil verb יַבִּיעַ (yabia’) means “to pour out; to emit; to cause to bubble; to belch forth.” The fool bursts out with reckless utterances (cf. TEV “spout nonsense”).