Art thou a king then? — The sentence is both a question and an inference from the word “kingdom” of the previous verse. There is a strong emphasis, and it may be sarcasm, expressed in the pronoun, “Does it not follow then that Thou art a king?”
Thou sayest that I am a king. — Or, perhaps, Thou sayest; for I am a king. (Comp. Matthew 26:25.)
To this end was I born, and for this cause came I into the world. — Better, Unto this end have I been born, and unto this end am I come unto the world. Our translators have rendered the same Greek words by different English words — “To this end,” “for this cause,” intending probably that the first phrase should be understood of the words which precede, and the second of those which follow: “To this end (that I may be a king) was I born, and for this (that I may bear witness unto the truth) came I into the world.” Had this been the meaning, it would have been almost certainly expressed by the usual distinction in Greek; and in the absence of any such distinction, the natural interpretation is, “To be king have I been born, and to be a king came I into the world, in order that I may bear witness unto the truth.” The birth and the entrance into the world both refer to the Incarnation, but make emphatic the thought that the birth in time of Him who existed with the Father before all time, was the manifestation in the world of Him who came forth from the Father. This thought of “coming into the world” is frequent in St. John. (Comp. especially John 10:36; John 16:28.)
That I should bear witness unto the truth. — Comp. Note on John 1:8. He has indeed a kingdom, and He came into the world to be a king; but His rule is that of the majesty of Truth, and His kingdom is to be established by His witness of the eternal truth which He had known with His Father, and which He alone could declare to man. (Comp. Notes on John 1:18; John 16:13.) He came to be a witness — a martyr — to the truth, and to send forth others to be witnesses and martyrs to the same truth, through the Holy Spirit, who should guide them into all truth. Such was His kingdom; such the power by which it was to rule. It was not of this world: it possessed neither land nor treasury, neither senate nor legions, neither consuls nor procurators; but it was to extend its sceptre over all the kingdoms of the earth.
Every one that is of the truth heareth my voice. — He has spoken of His kingdom. Who are its subjects, and what its power over them? Every one is included who, following the light which God has placed in his soul, comes to “the true Light which lighteth every man;” who, made in the image of God, and with capacities for knowing God, seeks truly to know Him; every one who, in an honest and true heart, is of the truth, and-therefore hears the voice of Him who is the Truth. The thought is familiar to us from the earlier Chapter s of the Gospel. (Comp. e.g., John 3:21; John 7:17; John 8:47; John 10:16.)