Matthew 12:36

Every idle word - Ρημα αργον, a word that does nothing, that neither ministers grace nor instruction to them who hear it. The word αργον corresponds to the Hebrew שוא shave, which signifies not only vain or empty, but also wicked and injurious, such as a false testimony against a neighbor, compare Deuteronomy 5:11, Deuteronomy 5:20. Add to this, that Symmachus translates פגול piggul, polluted, Leviticus 19:7, by the very Greek word in the text. It was to explain this ambiguous meaning of the word, that ten MSS. have changed αργον into πονηρον, evil. Our Lord must be understood here as condemning all false and injurious words: the scope of the place necessarily requires this meaning.

But I say unto you ... - Christ closes this address to his malignant and wicked hearers by a solemn declaration that for these things God would bring them into judgment. Therefore. They who had spoken so malignantly against him, could not escape.

Idle word - This literally means a vain, thoughtless, useless word; a word that accomplishes no good. Here it means, evidently, "wicked, injurious, false, malicious, for such" were the words which they had spoken.

12:36 Ye may perhaps think, God does not so much regard your words.But I say to you - That not for blasphemous and profane words only, but for every idle word which men shall speak - For want of seriousness or caution; for every discourse which is not conducive to the glory of God, they shall give account in the day of judgment.