Proverbs 30:32
"If thou hast done foolishly in lifting up thyself, or if thou hast thought evil, lay thine hand upon thy mouth."
Cross References (ranked by relevance)
Job 21:5
Mark me, and be astonished, and lay your hand upon your mouth.
Proverbs 26:12
Seest thou a man wise in his own conceit? there is more hope of a fool than of him.
Job 40:4
Behold, I am vile; what shall I answer thee? I will lay mine hand upon my mouth.
Romans 3:19
Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God.
Proverbs 17:28
Even a fool, when he holdeth his peace, is counted wise: and he that shutteth his lips is esteemed a man of understanding.