When parents are not in fellowship with God and one another, that home is opened up to the devil's attack as it was with Cain and Abel. The religion of Cain serves as a warning to us today if we exhibit Cain's anger against other believers who don't see eye-to-eye doctrinally or have the fire of God on their lives. And from the very beginning, God preached a gospel of victory that sin is not to master you.
