John Calvin on John 16:3

3. And they will do these things. Not without good reason does Christ frequently remind the apostles of this consideration, that there is only one reason why unbelievers are so greatly enraged against them. It is, because they do not know God. And yet this is not said for the purpose of extenuating their guilt, but that the apostles may boldly despise their blind fury; for it often happens that the authority which wicked men possess, and the luster which shines in them, shake modest and pious minds. But Christ, on the other hand, enjoins his followers to rise with holy magnanimity, to despise their adversaries, who are impelled by nothing else than error and blindness; for this is our wall of brass, when we are fully persuaded that God is on our side, and that they who oppose us are destitute of reason. Again, these words remind us, what a serious evil it is not to know God, since it leads even those who have murdered their own parents to expect praise and approbation for their wickedness.