Let another man praise thee, and not thine own mouth.
Self-boasting
Self-boasting is always a source of weakness as well as a revelation of vanity. In vanity there is no substance; it is idle breath, it is foolish vapour. When a man is left to praise himself it is evident that he has lived an inverted life, not a life full of blessedness and comfort in relation to other men. The sun does not praise himself, but under his splendour and warmth men look up and say how pleasing a thing it is for the eyes to behold the light. On the other hand, we must beware of a very common and perilous deceit. There is a sense in which every man ought to be able to praise himself; otherwise the applause of the public will be left by him to be a mockery and a lie. Our own heart should not condemn us. The psalmist was wont to glory in his integrity, and to point to it as his refuge in the time of misunderstanding. (J. Parker, D.D.)