In Psalm 19:14 the writer prays: “May the words of my mouth and the meditation of my heart be pleasing in your sight, O Lord, my Rock and my Redeemer.”
Throughout the wisdom literature, there is an emphasis on the danger of unguarded speech. In the New Testament, James writes: “No man can tame the tongue; it is a restless evil, full of deadly poison (4:8).
In Psalm 141, the writer is conscious of the influence of others on his speech and this is the focus of his prayer: “Set a guard over my mouth, O Lord; keep watch over the door of my lips. Let not my heart be drawn to that which is evil, to take part in wicked deeds with men who are evildoers; let me not eat of their delicacies.”
What comes out of your mouth often smells a lot like what you take in. When your companions are those whose speech is perverse, you will soon sound like them. It’s the way things work.
Here’s an exercise: Make a list of all the words your parents would have objected to when you were young. Which of those words now reside in your vocabulary? If speech betrays the heart, purifying the heart will require excising from our vocabulary the “adult” words that never should have been there in the first place – words that have more in common with a pagan world than a pious one. You might also want to adopt the prayer of Psalm 141 in the purifying process.