Psalms 34:13

13.Keep thy tongue from evil The precept which David here delivers relates to a virtue which is very rare, namely, that we should be truthful and free from deceit in our discourse. Some, indeed, understand it in a much more extended sense, supposing that slander is condemned in this first clause. But it seems to me more simple, and more to the purpose, to understand this as of the same import with what he repeats in the second clause, that we should not speak deceitfully with our neighbors, so as that our words may prove the means of ensnaring them. And since nothing is more difficult than to regulate our discourse in such a manner as that our speech may be a true representation of our hearts, David calls upon us to exercise over it a strict and watchful control, not suffering it to run riot, lest it should prove the occasion of our deceiving others.