Therefore, laying aside falsehood, speak truth each one of you with his neighbor, for we are members of one another. Be angry, and yet do not sin; do not let the sun go down on your anger, and do not give the devil an opportunity.
He who steals must steal no longer; but rather he must labor, performing with his own hands what is good, so that he will have something to share with one who has need. Let no unwholesome word proceed from your mouth, but only such a word as is good for edification according to the need of the moment, so that it will give grace to those who hear.
Do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption. Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice. Be kind to one another, tender-hearted, forgiving each other, just as God in Christ also has forgiven you.
New American Standard Bible, 1995 Edition
One of the most confirming things about our supernatural origins is that as humans we are the only creatures that can make promises. Now, notice, I said “creatures,” or created beings. God is eternal and self-sufficient. And because God is holy and we are sinful, we also have the ability to break promises: to lie.
Unrighteous anger is a terrible weapon in the hands of a Christian. We are allowed to be angry at sin, but when we misuse it, we are stealing something from God.