And the tongue is a fire, a world of iniquity. The tongue is so set among our members that it defiles the whole body, and sets on fire the course of nature; and it is set on fire by hell. For every kind of beast and bird, of reptile and creature of the sea, is tamed and has been tamed by mankind. But no man can tame the tongue. It is an unruly evil, full of deadly poison. With it we bless our God and Father, and with it we curse men, who have been made in the similitude of God. Out of the same mouth proceed blessing and cursing. My brethren, these things ought not to be so. (James 3:6-10)
St John Chrysostom offers some thoughts about the human tongue:
“The devil tries to hurt us in every way, but especially through our tongues and mouths. He finds no instrument so suitable for deceiving and destroying us as an undisciplined tongue and a mouth that is never closed. From these sources come many disasters and grievous accusations against us. An inspired writer has made it clear how easy it is to sin by the tongue when he said: Many have fallen by the sword, but not so many as have perished by the tongue (Sirach 28:18).
And showing how serious this kind of sin is, the same inspired writer says again: a slip from the pavement rather than a slip of the tongue (Sirach 20:18). What he means is this: It is better, he says, to fall and shatter the body rather than utter such a word as destroys the soul. He not only speaks of the sin but he also exhorts us to take great care not to be tripped up when he says: Make a door and bars for your mouth (Sirach 28:24-25). Of course, he did not literally mean we make ready doors and bars, but he did mean for us to be very careful to close our tongue off from absurd speech.” (BAPTISMAL INSTRUCTION, p 141)
Chrysostom goes on to specify some sinful things that come from the mouth and tongue:
“The things which make the mouth filthy are slander, blasphemy, railing words, angry words, obscene words, words which provoke laughter, and ribald words.” (BAPTISMAL INSTRUCTION, pp 295-296)
The Lord Jesus said: For it is from within, from the human heart, that evil intentions come: fornication, theft, murder, adultery, avarice, wickedness, deceit, licentiousness, envy, slander, pride, folly. (Mark 7:21-22)
If anyone among you thinks he is religious, and does not bridle his tongue but deceives his own heart, this one’s religion is useless. (James 1:26)