Solomon used the word rash several times when giving counsel to his sons. He wasn't addressing skin inflammations or bodily eruptions resulting from exposure to irritants. He was specifically identifying the verbal miscalculation of speaking in a thoughtless, impetuous manner. Rash words use indiscreet language usually motivated by emotional impulses. They are spoken in anger, disappointment, failure, passion, happiness or any other feeling that ignites our responsiveness. His description of rash words is portrayed, as is much of his advice, with very graphic and descriptive language---
There is one whose rash words are like sword thrusts, but the tongue of the wise brings
Proverbs 12: 18, ESV
Several conclusions are obvious in his verbiage. One, like a sword thrust, rash words are unexpected and dangerous to the one receiving them. Now, I've never been in a fencing match and don't understand the posture, footwork and discipline of attacking and parrying. But, outside the martial arts and scripted fencing maneuvers, the sword thrust of Solomon's day would have been instantaneous responses to being attacked, moves in preservation of self. Like the sword thrust, rash words catch the receiver of them off-guard. And, they can be deadly.
Two, rash words are outside the scope of wisdom in that they have not been previously thought or prepared. Usually they are spoken in the heat of the moment, an outburst triggered by an emotional outburst, an instant response. In the third place, Solomon indicated that words spoken in an ill-advised, foolhardy manner are designed to injure, hurt, or destroy rather than heal. They are unschooled and are therefore uttered without preparation or consideration.
In the book of Ecclesiastes Solomon noted Israel's history of speaking rash words to their Creator God. There were numerous occasions in their past when the people of Israel responded to God's discipline with promises and commitments they could not keep. One instance was under the leadership of Joshua as they prepared to enter the Land of Promise (see Joshua 24). Joshua challenged them to serve the Lord and obey him as they occupied the land God had promised to Abraham. In response to his urging they swore to serve and obey God (see Joshua 24: 16; 21; 24). Of course, the Book of Judges repeatedly proves that their promises were rash words, spoken under the stress of their circumstances. They did evil in the sight of the Lord and served other gods. So, in Ecclesiastes he wrote---
Be not rash with your mouth, nor let your heart be hasty to utter a word before God,
for God is in heaven and you are on earth. Therefore let your words be few.
Ecclesiastes 5:2, ESV
How often life circumstances are the catalysts for us to blurt our rash words, even to God! As mentioned by Solomon wisdom should bracket our words. At times a wise spirit will dictate silence rather than an explosion of words without thought, rash words that further complicate an emotional situation. It certainly is the case in today's fake news culture, especially visible in social media right now. The Covid-19 pandemic, political maneuvering, cultural dynamics, economic trends, gender discussions, and so many other current news items have the fire to inflame our verbal machinery. Rash words should not be our response to them.
This is a hard one for me, I must confess. My personal strength array places deliberative and analytical at the very bottom. Wisely thinking through my words isn't an automatic setting for me. Meaning, that I should be patient and thoughtful when replying to the various stimuli of every day. And, prayerful too. Prudence is the cure for rash words and actions.
Let's pray for caution in our language. Rash words seldom solve anything.