Oh, how the mouth of the foolish boasts. This is seen again and again in our society. In fact, we now have a whole type of speech devoted to prideful talk. Trash-talking is popular today among those in sports. The dangerous thing is that this type of talk is slowly morphing its way into regular life as well. This will not bode well for our society - as pride is never a good thing among the conversations of men.
Biblically there is a great picture of this very verse. When David fought the Philistine champion, Goliath, there was some serious "trash-talking" going on from Goliath. He laughed at David and disdained him publically in front of all the troops that day. HE bellowed that he would give little David to the birds of the air when he killed him. You can hear this boast echoing through the valley just as 40 previous boasts had done for the 40 days he had been bragging about his pwoer and abilities. In his mouth was a rod for his back. The literal translation of this phrase is "rod of pride." Interesting that the Hebrew language would have such a phrase. But it only shows the way that pride does give God a rod which He will use upon our backs to discipline us for our arrogance. Goliath's boasts ceased - because he lost his head - literally. He thought he could destroy David with little effort. In the end - his arrogant words were a rod of pride that struck him as a rock sunk into his forehead. As the sword severed his neck - Goliah - once a hero and champion - would forever be known for his defeat at the hands of a ruddy little shepherd with a sling, stone, and a trust in the living God.
The wise have lips that protect them. They are careful about what they say - and how they say it. The old WWII phrase "loose lips, sink ships," is in order for the wise man. Far too many have not watched what they say and have paid for it dearly. David is a good example in this story as well. He did not go out and make empty boasts. He did not try to one-up Goliath at his "trash-talking" game. He simply referred to his God and reminded Goliath that though he came with superior "human" firepower - David relied upon an omnipotent God to win the day. David's words were far from proud and arrogant. They were humble words that relied upon Jehovah God for strength. In the end, David's words protected him from not only arrogance and presumption - but also from Goliath's attack.
We need to be wise - and watch what we say. It is protection for us to stay as close to what the Scriptures tell us as possible. Our protection is given to us by a God who loves to act strongly on behalf of those who look to Him. Rather than have our words be the very whip that disciplines us - they become a shield that keeps us from harm.