The father whose sons you are is the Devil; and you desire to do what gives him pleasure. He was a murderer from the beginning, and does not stand firm in the truth–for there is no truth in him. Whenever he utters his lie, he utters it out of his own store; for he is a liar, and the father of lies.
We are not to resemble Cain, who was a child of the Evil one and killed his own brother. And why did he kill him? Because his own actions were wicked and his brother's actions righteous.