John Calvin Commentary John 18:37

"Pilate therefore said unto him, Art thou a king then? Jesus answered, Thou sayest that I am a king. To this end have I been born, and to this end am I come into the world, that I should bear witness unto the truth. Every one that is of the truth heareth my voice." — John 18:37 (ASV)

You say that I am a king. Although Pilate had already learned from the previous answer that Christ claims some sort of kingdom for himself, Christ now asserts the same thing more firmly. Moreover, not satisfied with this, he makes an additional statement, which serves as a seal, so to speak, to confirm what he had said. Therefore, we infer that the doctrine concerning Christ’s kingdom is of no ordinary importance, since he has deemed it worthy of such a solemn affirmation.

For this cause was I born, that I may bear witness to the truth. This is, no doubt, a general sentiment, but it must be viewed in relation to the place it holds in the present passage. The words mean that it is natural for Christ to speak the truth. Next, they mean that he was sent for this purpose by the Father. Consequently, this is his specific office. Therefore, there is no danger that we will be deceived by trusting him. For it is impossible that he who has been commissioned by God, and whose natural disposition leads him to maintain the truth, will teach anything that is not true.

Every one that is of the truth. Christ added this not so much for the purpose of exhorting Pilate (for he knew that he would gain nothing by doing so) as for defending his doctrine against the base reproaches that had been cast on it. It was as if he had said, “It is charged against Me as a crime that I have asserted that I am a king; and yet this is an unquestionable truth, which is received with reverence and without hesitation by all who have a correct judgment and a sound understanding.” When he says that they are of the truth, he does not mean that they naturally know the truth, but that they are directed by the Spirit of God.