Context Ephesians 4:17-32
Bitterness is caused by not offering grace or forgiveness. It leads to wrath, insult, and slander. We must remove this from ourselves. We can do so by being compassionate and offering grace to others just as our Heavenly Father offered grace to us. Doing this benefits others, but it also benefits ourselves. For bitterness will rot our bones.
“All bitterness, anger and wrath, shouting and slander must be removed from you, along with all malice. And be kind and compassionate to one another, forgiving one another, just as God also forgave you in Christ.”