TSK · Genesis 4:1

Adam knew his wife again. She gave birth to a son, and named him Seth, "for God has appointed me another child instead of Abel, for Cain killed him."

Now therefore kill every male among the little ones, and kill every woman who has known man by lying with him.

unlike Cain, who was of the evil one, and killed his brother. Why did he kill him? Because his works were evil, and his brother's righteous.