John is strongly reminding us that, as believers in Christ, we belong to an utterly different realm to the majority of men : we are children of God, not children of the Devil. The unbelievers around us have a completely different allegiance. The Christian’s holiness of life is a testimony against the unbeliever. We must not marvel, therefore, if men hate us; let us remember how Cain hated Abel.
But how should we respond to this hostility? We dare not respond with more hatred, for that is the spirit of murder, but we must love our brethren, our neighbours, and even our sworn enemies longing that they might come to know salvation. We must do what our Lord did : endure the hatred, whilst preaching the Gospel.
Our Lord gave up His life for His enemies, and we are called to follow His example in enduring their hostility, in loving even our persecutors, and weeping over them, that they might hear the gospel and be saved. We must assault Satan’s strongholds with the gospel. We must never adopt the attitude, I am saved; let the world get on with it, and go to hell. That was not the attitude of our Lord, who looked upon the multitudes with deep compassion, as sheep without a shepherd, for our Lord is “not willing that any should perish, but that all should come to repentance” (2 Peter 3:9), and we must follow His example, whatever the cost.