Lay thine hand upon thy mouth - The act expresses the silence of humiliation and repentance after the sin has been committed, and that of self-restraint, which checks the haughty or malignant thought before it has passed even into words.

If thou hast done foolishly - And who has not, at one time or other of his life?

Lay thine hand upon thy mouth - Like the leper; and cry to God, Unclean! unclean! and keep silence to all besides. God will blot out thy offense, and neither the world nor the Church ever know it, for he is merciful; and man is rarely able to pass by a sin committed by his fellows, especially if it be one to which himself is by nature not liable or inclined.

If thou hast done foolishly in lifting up thyself,.... Against a king, against whom there is no rising up; by speaking evil of him, or rebelling against him; which is acting a foolish part, since it brings a man into troubles and difficulties inextricable; or by self-commendation, which is the height of folly, and the fruit of pride; or carried it in such a haughty and overbearing manner to others, as to provoke to wrath and anger;

or if thou hast thought evil; purposed and designed it, and contrived the scheme of doing it, though not yet put in execution; though folly is not actually committed, yet since the thought of it is rain, care should be taken to prevent it;

lay thine hand upon thy mouth: think again before the thing resolved on is done; as studious and thoughtful men put their hand to their mouth, when they are deeply considering any affair before them: or put a stop to the design, let it go no further; what has been thought of in the mind, let it never come out of the mouth, nor be carried into execution; stifle it in the first motion: or if this respects a foolish action done, as it also may, since it stands connected with both clauses, then the sense is, be silent; do not pretend to deny the action, nor to excuse it; nor to say one word in the defence of it; nor to lay the blame upon others; and much less to calumniate and reproach such who faithfully reprove for it; take shame to thyself in silence, and repent of the iniquity done. Aben Ezra thinks these words are said to Ithiel and Ucal; but rather, to any and everyone, to all that should hear and read these proverbs. The Targum is,

"do not lift up thyself, lest thou be foolish; and do not stretch out thine hand to thy mouth.''

Another proverb, the last of Agur's "Words" which exhorts to thoughtful, discreet demeanour, here follows the proverb of self-conscious, grave deportment:

32 If thou art foolish in that thou exaltest thyself,

     Or in devising, - put thy hand to thy mouth!

33 For the pressure on milk bringeth forth butter,

     And pressure on the nose bringeth forth blood,

     And pressure on sensibility bringeth forth altercation.

Lwenstein translates Proverbs 30:32 :

Art thou despicable, it is by boasting;

Art thou prudent, then hold thy hand on thy mouth.

But if זמם denotes reflection and deliberation, then נבל, as its opposite, denotes unreflecting, foolish conduct. Then בּהתנשּׂא ne by boasting is not to be regarded as a consequent (thus it happens by lifting thyself up; or: it is connected with boasting); by this construction also, אם־נבלתּ must be accented with Dechi, not with Tarcha. Otherwise Euchel:

Hast thou become offensive through pride,

Or seems it so to thee, - lay thy hand to thy mouth.

The thought is appropriate,

(Note: Yet the Talmud, Nidda 27a, derives another moral rule from this proverb, for it interprets זמם in the sense of זמם equals חסם, to tie up, to bridle, to shut up, but אם נבלת in the sense of "if thou hast made thyself despicable," as Lwenstein has done.)

continued...

If thou hast done foolishly in lifting up thyself, or if thou hast thought evil, lay thy hand {p} upon thy mouth.

(p) Make a stay and continue not in doing evil.

30:32 Thought - Designed any injury against thy neighbour. Lay thine hand - Do not open thy mouth to excuse it, but repent of it, and do so no more.

32. As none can hope, successfully, to resist such a king, suppress even the thought of an attempt.

lay . hand upon thy mouth-"lay" is well supplied (Jud 18:19; Job 29:9; 40:4).

30:24-28. Four things that are little, are yet to be admired. There are those who are poor in the world, and of small account, yet wise for their souls and another world. 29-33. We may learn from animals to go well; also to keep our temper under all provocations. We must keep the evil thought in our minds from breaking out into evil speeches. We must not stir up the passions of others. Let nothing be said or done with violence, but every thing with softness and calmness. Alas, how often have we done foolishly in rising up against the Lord our King! Let us humble ourselves before him. And having found peace with Him, let us follow peace with all men.