He that keepeth his mouth keepeth his life - How often have the foolish, headstrong, and wicked, forfeited their lives by the treasonable or blasphemous words they have spoken! The government of the tongue is a rare but useful talent.
But he that openeth wide his lips - He that puts no bounds to his loquacity, speaks on every subject, and gives his judgment and opinion on every matter. It has often been remarked that God has, given us two Eyes, that we may See much; two Ears, that we may Hear much; but has given us but One tongue, and that fenced in with teeth, to indicate that though we hear and see much, we should speak but little.

He that keepeth his mouth keepeth his life,.... He that keeps his mouth shut keeps it as with a bridle; keeps it from speaking things of other persons, particularly of such as are in high places, of kings and princes, and civil magistrates: he keeps himself quiet and comfortable; keeps himself from many troubles, which otherwise he would come into; keeps his life from danger, to which it would be exposed, should he speak evil of dignities, or give himself the freedom, as some do, whereby they are brought to an untimely end; see Proverbs 18:21; besides, persons ought to be careful of their words, since by them a man will either be justified or condemned hereafter, Matthew 12:37;
but he that openeth wide his lips shall have destruction; or "consternation" (x): he that is rash and inconsiderate, hasty with his lips, a talkative man; that speaks freely everything that comes into his mind, regardless of the characters of men, or consequences of things; is often brought into frights and fears, through the menaces and threatenings of men in power, whose characters he has made too free with, and oftentimes is brought to ruin and destruction: so he, whose throat is as an open sepulchre, belching out filthy words, horrid oaths, curses, and imprecations, destruction is near him, even in all his ways; and the man of sin, that opens his mouth in blasphemy against God, and his tabernacle, and his saints, shall go into perdition, Revelation 13:5.
(x) "consternatio", Mercerus, Cocceius, Michaelis; "terrebitur", Tigurine version.

He that thinks before he speaks, that suppresses evil if he have thought it, keeps his soul from a great deal both of guilt and grief. Many a one is ruined by an ungoverned tongue.

He . . . mouth . . . life--because evil speeches may provoke violence from others.
he that openeth wide his lips shall have destruction--On last clause, compare Proverbs 10:14.

3 He that guardeth his mouth keepeth his soul;
He that openeth his lips, to him it is destruction.
3a is extended in Proverbs 21:23 to a distich. Mouth and soul stand in closest interchangeable relation, for speech is the most immediate and continuous expression of the soul; thus whoever guards his mouth keeps his soul (the Venet., with excellent rendering of the synonym, ὁ τηρῶν τὸ στόμα ἑαυτοῦ φυλάσσει τὴν ψυχὴν ἑαυτοῦ), for he watches that no sinful vain thoughts rise up in his soul and come forth in words, and because he thus keeps his soul, i.e., himself, safe from the destructive consequences of the sins of the tongue. On the contrary, he who opens wide his lips, i.e., cannot hold his mouth (lxx ὁ δὲ προπετὴς χείλεσιν), but expresses unexamined and unconsidered whatever comes into his mind and gives delight, he is destruction to himself (supply הוּא), or to him it is destruction (supply זאת); both interpretations are possible, the parallelism brings nearer the former, and the parallel Proverbs 18:7 brings nearer the latter. פּשׂק means to spread (Schultens diducere cum ruptura vel ad rupturam usque), here the lips, Pih. Ezekiel 16:25, the legs, Arab. fashkh, farshkh; vid., regarding the R. פש, to extend, to spread out, Fleischer in the supplements to the A. L. Z. 1843, col. 116. Regarding the Mishle word מחתּה, vid., under Proverbs 10:14.