1 John 3:10-12, 15

Here is how God’s children can be clearly distinguished from the children of the Evil One. Anyone who does not demonstrate righteousness and show love to fellow believers is not living with God as his source. The beautiful message you’ve heard right from the start is that we should walk in self-sacrificing love toward one another. We should not be like Cain, who yielded to the Evil One and brutally murdered his own brother, Abel. And why did he murder him? Because his own actions were evil and his brother’s righteous.

Everyone who keeps hating a fellow believer is a murderer, and you know that no murderer has eternal life residing in him.