Time and again God brings me to my knees over my heart attitude expressed out of my mouth. More than once, God has led me to fast of negative, critical, judgmental, and complaining words. Why a fast of words? Is that a legitimate application of fasting? The Hebrew word "fast" means to cover the mouth. For me, it is harder to fast from words than from food. Abstaining from negative words may be as powerful as fasting from food, because it is a particular battlefield for most of us.
A fast of words is one of the fasts in Isaiah 58. Isaiah 58:9b lists not pointing fingers in judgment and no wicked words as conditions of great blessings listed in verses 10b-12.
The first time God led me to fast for 40 days of all negative, complaining, critical, and judgmental words was one of the hardest experiences of my Christian life. The problem is not my mouth but my heart. Proverbs 4:23 says "Keep your heart with all diligence, for out of it spring the issues of life
About two weeks into my fast, I was treated haughtily at a store. As I left the store, I said to myself, "I'll just take my business elsewhere. That is the second time she has had an attitude with me." Immediately I heard in my spirit, "No, you are the one with the attitude." I wanted to fall to my knees on the sidewalk, crying out, "Woe is me! I am ruined! For I am a man of unclean lips, and I live among a people of unclean lips (Isa. 6:5). O God, take a coal from the altar and purge this wicked heart of mine." God showed me that He was dealing with a root of pride (Isa. 57:15, 1 Peter 5:5-6). I was puffed up, with no sense of my own spiritual need.
I struggled for a while in this fast of words, but God softened and sweetened my heart. After that season, I felt like a dog with an invisible electric fence. Every time I opened my mouth to say anything critical, I would get a check from my loving Father. Later I reviewed my prayer notebook and was amazed at how many Scriptural insights God gave me during that time. God was being faithful to reveal more of Himself.
For a while I have been keenly aware of living with a grateful heart, thankfully noting God touches great and small. Recently I read a devotional on a thankful heart. The author set up a contrast between thankfulness and negativity. He quoted Paul, when he said "And do not grumble, as some of them did and were killed by the destroyer" (1 Corinthians 10:10). That puts the choice all of us have in very stark contrast: choose thankfulness in all things or choose sides with destruction.
Ask God if He is leading you to do a forty-day fast of critical, judgmental, negative, complaining, gossiping words. You may be amazed what God will do through it. At the very least, your family and friends may be amazed at the change in you, from destruction to blessing.