“Be angry, and do not sin”: do not let the sun go down on your wrath, nor give [a]place to the devil.
- Ephesians 4:26-27
Anger is an expression or outburst of displeasure or unpalatable emotions, and is usually a response to a perceived provocation, threat or hurt. Anger is not always a sin, but has a threshold, which when exceeded, becomes sin. Jesus expressed a righteous indignation over the people that turned the temple of God to a market place (John 2:13-17), without committing sin in the process. Let's consider when anger becomes a sin.
When anger is allowed to linger and lead to malice.
The Bible specifically says "...do not let the sun go down on your wrath." When anger is dwelt upon for too long, it generates into malice, and sometimes hatred. This is no way to live as a child of God.
When the angry one refuses to be pacified or holds a grudge.
This is a very dangerous thing to do. When an offender apologizes for a wrong done and the offended refuses to accept the apology, but instead decides to hold a grudge, or with the intention of retaliation, this could lead to sin. Such action could generate into physical hurt or material damage.
The sons of Jacob are typical examples of this. Dinar, their sister was violated by Sheckem, son of Hamor. They were pacified and pretended to have forgiven the offender. They however held this hurt for long until they avenged their sister's rape by killing the offender and his clan. (Genesis 34: 1-25).
When anger is displayed hastily or blown out of proportion
At times, a person just wants to quickly express displeasure over a wrong done, so as to give no room to any apology, or when an offense is exaggerated, and recompensed by the supposed offended.
Do not hasten in your spirit to be angry, For anger rests in the bosom of fools.
- Ecclesiastes 7:9
When Anger is motivated by pride
Some people express anger as a result of a position superior to others, or they are connected to positions or people who can help them deal with supposed offenders. A boss for instance can over react to a subordinate's actions and take irrational actions against such. A policeman can also by reason of his uniform lay flimsy or false claims on an helpless individual, just to show that he has the means of hurting such a one.
The anger that Jesus displayed in John 2:13-17 was borne out of love for God, orderliness, and holiness. When angry, it is wise to restrain from taking hasty actions. Moses' uncontrolled anger denied him the opportunity of leading the Israelites into the land of promise, after several breakthroughs. Do not let anger rob you of your salvation. Be angry, but sin not!