Proverbs - Lay your hand upon your mouth!

We must bridle and suppress our own passion, and take shame to ourselves, whenever we are justly charged with a fault, and not insist upon our own innocency: If we have lifted up ourselves, either in a proud conceit of ourselves or a peevish opposition to those that are over us, if we have transgressed the laws of our place and station, we have therein done foolishly. Those that magnify themselves over others or against others, that are haughty and insolent, do but shame themselves and betray their own weakness. Nay, if we have but thought evil, if we are conscious to ourselves that we have harboured an ill design in our minds, or it has been suggested to us, we must lay our hand upon our mouth, that is:

1) We must humble ourselves for what we have done amiss, and even lie in the dust before God, in sorrow for it, as Job did, when he repented of what he had said foolishly (Job 40:4 ) and as the convicted leper, who put a covering upon his upper lip.
 If we have done foolishly, we must not stand to it before men, but by silence own our guilt, which will be the best way of appeasing those we have offended.
2) We must keep the evil thought we have conceived in our minds from breaking out in any evil speeches. Do not give the evil thought an imprimatur - a license; allow it not to be published; but lay thy hand upon thy mouth; use a holy violence with thyself, if need be, and enjoin thyself silence; as Christ suffered not the evil spirits to speak. It is bad to think ill, but it is much worse to speak it, for that implies a consent to the evil thought and a willingness to infect others with it. [emphasis mine]

 extract from Matthew Henry Commentary