You need the whole context here to get this is instruction to Christians on how to treat one another . The reference is to Cain and Able . Read the chapter a few times and you will get it
. I think the message is don't let any hate take root in your heart for your brethren . I needed to hear this message recently .
1 John 3:15 Context
12Not as Cain,
who was of that wicked one, and slew his brother. And wherefore slew he him? Because his own works were evil, and his brother's righteous.
13Marvel not, my brethren, if the world hate you.
14We know that we have passed from death unto life, because we love the brethren. He that loveth not
his brother abideth in death.
15Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him. 16Hereby perceive we the love
of God, because he laid down his life for us: and we ought to lay down
our lives for the brethren.
17But whoso hath this world's good, and seeth his brother have need, and shutteth up his bowels
of compassion from him, how dwelleth the love of God in him?
18My little children, let us not love in word, neither in tongue; but in deed and in truth.