John Gill 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)

Pilate therefore said to him
Upon this free and full declaration of Christ, concerning his kingly office, and the nature of his kingdom: are you a king then?

Or you are a king then: for, from his having a kingdom, it might be very justly inferred that he was a king: Jesus answered, you say that I am a king; and which was very rightly said; and Christ by these words owns and confesses, that he was one: adding, to this end was I born, and for this cause came I into the world, that I should bear witness to the truth.

The end of Christ's being born, which was of a virgin, in a very miraculous manner, and of his coming into the world, which was by the assumption of human nature, among many other things, was to bear testimony to truth in general; to the whole Gospel, the word of truth, and every branch of it, which he brought with him, constantly preached in life, and confirmed by his death; and particularly to this truth, that he was a King, and had a kingdom in a spiritual sense.

Everyone that is of the truth; that is of God, belongs to the sheep of Christ, knows the truth as it is in Jesus, and is on the side of truth, and stands by it: hears my voice; the voice of his Gospel; and that not only externally, but internally; so as to approve of it, rejoice at it, and distinguish it; and the voice of his commands, so as cheerfully to obey them from a principle of love to him.