Matthew 12:36

“And I say to you, that every idle word that men shall speak, they will give account of them in the day of judgment.”

So men should beware. Let them just listen to their own words. For every word let slip when they are unguarded reveals what is in their hearts. A man can and will be judged by his words, especially those that he thinks are ‘off the record'. The ‘idle word' is not simply the word used in casual conversation, it is the word which is what it ought not to be, the word which would be better unspoken, the word spoken carelessly and thereby revealing what is really within. Thus at the judgment everything that a person has said will be brought into account in judging that person's heart. Let the Pharisees now take heed to their words, for by them they are revealing what they are in their hearts, and that is what they will be judged by. And the same is true for us all.