12:33-37 Men's language discovers what country they are of, likewise what manner of spirit they are of. The heart is the fountain, words are the streams. A troubled fountain, and a corrupt spring, must send forth muddy and unpleasant streams. Nothing but the salt of grace, cast into the spring, will heal the waters, season the speech, and purify the corrupt communication. An evil man has an evil treasure in his heart, and out of it brings forth evil things. Lusts and corruptions, dwelling and reigning in the heart, are an evil treasure, out of which the sinner brings forth bad words and actions, to dishonour God, and hurt others. Let us keep constant watch over ourselves, that we may speak words agreeable to the Christian character.
36. But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment—They might say, "It was nothing: we meant no evil; we merely threw out a supposition, as one way of accounting for the miracle we witnessed; if it will not stand, let it go; why make so much of it, and bear down with such severity for it?" Jesus replies, "It was not nothing, and at the great day will not be treated as nothing: Words, as the index of the heart, however idle they may seem, will be taken account of, whether good or bad, in estimating character in the day of judgment."