10 In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, nor is he who does not love his brother. 11 For this is the message that you heard from the beginning, that we should love one another, 12 not as Cain who was of the wicked one and murdered his brother. And why did he murder him? Because his works were evil and his brother’s righteous. 1 John 3:10-12
The manifestation of righteousness and holiness is love. We cannot claim we are truly in Christ if we do not love our brother or sister. Jesus was the personification of love in that He laid down His life for all humanity. Those who spit on Him, those who tortured Him, and those who blasphemed His name He laid down His life for them. If we are to truly claim we are in Christ then we must walk in love. This is only possible as we abide in Him.
Cain is a picture of one who is driven by wickedness. Able gave his sacrifice in righteousness and it was pleasing unto the Lord. Cain in jealousy of his brother desired and acted on the intention to kill his brother. Those who walk in hate and bitterness cannot be children of God.
There is a distinction on this earth between those who are children of God and those who are following after the wickedness of the world. Those who reject Jesus Christ and His Lordship have no answer for the bondage and curse of sin. But those who are in Christ have been set free. As we abide in Him we are transformed into His character and His image. In all that we do we are driven by love. This enables us to love those who are the toughest to love. For if we are truly children of God then we will be filled with His love, grace, and mercy.