But how can we distinguish whether we are separated from that wicked world, and have passed from death unto life?  Here John urges upon us again one of his fundamental tests of assurance.  We can know that we have passed from death unto life if we love the brethren.  In a certain sense, we are to love all men, even our enemies, in that we do them good and not evil, and are willing to aid them in their time of distress.  But there is a peculiar love between the children of God into which the world is not admitted.  While the command to love our neighbors as ourselves is universal, the great commandment of Christ that we love one another even as He loved us is for believers alone.  We should lay down our very lives for the sake of the brethren, John tells us later, for this is what Christ did for us.  If we have this deep affection, this self-sacrificing love, for those who are our brethren and sisters in Christ, then we should have every confidence that we have passed from death unto life.

The contrary is so for the man of whom this is not true.  The man who does not love his brother, regardless of his religious pretensions, abides in death.  So it was with Cain.  Cain was not an infidel, but a man so religious that he brought of the fruit of the ground for which he had toiled an offering unto God.  But the hypocrisy and wickedness of his heart was manifested when he slew his brother.  So it is with people enfolded in the bosom of the church, who can read their Bibles, talk religion, partake of the ordinances, and yet still cherish grudges and despite against other Christians.  They may be very religious outwardly, but the hatred they nourish towards God’s children shows that, in actuality, they are of their father the Devil.