[The events before Cain killed Abel]
…The Lord looked with favor on Abel and his offering, but on Cain and his offering He did not look with favor. So Cain was very angry, and his face was downcast. Then the Lord said to Cain, “Why are you angry? Why is your face downcast? If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must master it.”
— Genesis 4:4-7
Cain’s sin didn’t start when he attacked Abel, or even when he plotted the attack. Cain’s sin started when he submitted to the feeling of anger, rather than mastering over it. Anger in itself is not a sin. The same feeling that caused Cain to become the first murderer is the same feeling that could have been used to bring spiritual growth in his life, causing him to repent and worship God properly. Cain should have used that anger towards the positive act of repentance in humility, rather than attacking in pride.
When the feeling of anger wells up inside of you due to someone confronting you with a possible fault in your life, use that anger to act positively in humility so that you can grow from the experience. Do not lash out in pride.
Heavenly Father, help me use times of anger as an opportunity of growth, rather than a means to sin. Grant me the humility to master over my anger when sin is crouching at my door. In Jesus’ Name I pray, AMEN!