Being angry for the right reasons is not sin otherwise the bible would not have said “Be angry but sin not” (Ephesians 4; 26). In others words being angry is not sin (provided its being angry for the right reasons).
Cain was angry for the wrong reasons, which was sin to him (Genesis 4; 1-7), this article is not addressing that type of anger.
The bible makes it clear that during the earthly ministry of our Lord Jesus Christ, He did not sin (2 Corinthians 5; 21), so we have a clear basis confirming Ephesians 4;26. A person can be angry and not sin.
During the earthly ministry of our Lord Jesus Christ, Jesus got angry at “hardness of heart”.
Mark 3: 1- 5
And he entered again into the synagogue; and there was a man there which had a withered hand.
2 And they watched him, whether he would heal him on the sabbath day; that they might accuse him.
3 And he saith unto the man which had the withered hand, Stand forth.
4 And he saith unto them, Is it lawful to do good on the sabbath days, or to do evil? to save life, or to kill? But they held their peace.
5 And when he had looked round about on them with anger, being grieved for the hardness of their hearts, he saith unto the man, Stretch forth thine hand. And he stretched it out: and his hand was restored whole as the other.
There is always a genuine reason to feel grieved and angry. One of them is hardness of heart.
The book of Proverbs also gives a reason to justify anger.
Proverbs 25;23 KJV
23 The north wind driveth away rain: so doth an angry countenance a backbiting tongue.
23 The north wind scattereth abroad rains; and a sorrowful face destroyeth a tongue backbiting. (Like the north wind scattereth rains abroad; so an angry look destroyeth a backbiting tongue.)
So there is nothing wrong in being angry for the right reasons. Just make sure you don’t sin, and if you do, repent and ask the Lord to forgive you.
Heavens agenda in any situation is several steps up higher than what we are thinking. Kevin Zadai.