Hebrews 12:15 says, “Looking carefully lest anyone fall short of the grace of God; lest any root of bitterness springing up cause trouble, and by this many become defiled.” I have a great visual for how bitter roots defile. 

Years ago I tried to take out a bed of candytuft. I went to pull up one plant, only to discover that the roots went every which way. Roots are hidden. Bitterness is a covert sin. It seeps into all of our thought processes. 

Peter nailed Simon in Acts 8.9-24. Verse 22-23 is a perfect description of covert bitterness. It says, “Repent therefore of this your wickedness, and pray God if perhaps the thought of your heart may be forgiven you. For I see that you are poisoned by bitterness and bound by iniquity.”

The roots of bitterness are pulled up as we forgive the one or the circumstances that we are bitter against. Think of the words corrupt, decay, rotten, etc. One rotten apple hidden in a barrel will defile every apple around it.