1 John 3:11-15 (ESV)
For this is the message that you have heard from the beginning, that we should love one another. We should not be like Cain, who was of the evil one and murdered his brother. And why did he murder him? Because his own deeds were evil and his brother’s righteous. Do not be surprised, brothers, that the world hates you. We know that we have passed out of death into life, because we love the brothers. Whoever does not love abides in death. Everyone who hates his brother is a murderer, and you know that no murderer has eternal life abiding in him.
The story of Cain and Abel is the first of many stories in the Bible and human history of anger leading to murder, leading to coverup, leading to discovery. Cain killed his brother because he had evilness in his heart. He killed him and then buried him. Abel’s blood cried out from the ground for vengeance:
Genesis 4:10 (ESV)
And the LORD said, “What have you done? The voice of your brother’s blood is crying to me from the ground.
Imagine all the blood of mankind crying out from the ground for vengeance by God on those that slayed them. That is what is going to take place in the end times. God will bring vengeance upon those who kill. But we should note that according to the above verse the killing was proceeded by envy and anger. Jesus made it clear that murder begins with anger:
Matthew 5:21-22 (ESV)
“You have heard that it was said to those of old, ‘You shall not murder; and whoever murders will be liable to judgment.’ But I say to you that everyone who is angry with his brother will be liable to judgment; whoever insults his brother will be liable to the council; and whoever says, ‘You fool!’ will be liable to the hell of fire.
Killing begins in the heart and God sees that as just as egregious as murder. What John is telling us in the above passage is that we were to not be like Cain. We are to, instead, love with unconditional love, as God does for us. If we have anger in our hearts we are not loving our brother. Note again how John states it:
1 John 3:14b-15)
Whoever does not love abides in death. Everyone who hates his brother is a murderer, and you know that no murderer has eternal life abiding in him.
The evidence of our abiding in Him is that anger and hate are not abiding in us.