Genuine love of Jesus involves making an effort to keep God’s commandments. Particularly the commandment of brotherly love, following the example of Christ who went as far to die for us. The persecutions and difficulties of a follower of Christ inevitably meets up should never shake his faith or discourage him. On the contrary, they should give him an opportunity to show his faith and to be consoled and comforted by the Holy Spirit.
In light of the apparent triumph of sin, Jesus teaches that there can be no agreement between himself and the sinful world: he who lives in sin hates the light (cf. 3:19-20). For this reason Christ has been, and the apostles will be, persecuted. Those who deny Jesus would not have sinned if he had not revealed himself through his works, if the Light had not overcome the darkness; but now they have no excuse; the rejection of Christ is the rejection of God’s truth (cf. Ps 35:19).