Jesus answered and said unto them,
Though I bear record of myself, yet my record is true: for I know from where I came, and where I go; but you cannot tell from where I come, and where I go.
All Commentaries on John 8:14 Go To John 8
Cyril of Alexandria
AD 444
On Christ saying that He is what He is by Nature and truly (for He openly declared, I am the Light of the world) the multitude of the Pharisees unrecking of danger deemed that He spake falsely. For in their exceeding folly they knew not that when some set forth their own nature and tell what is essentially inherent in them, we shall not, if we think aright, suppose that they do so out of boasting, nor shall we say that they are bent on hunting vain-glory, but rather that they declare what they really are. As for example we say that when an angel pointing out his own nature says, I am an angel; when a man shewing what he is says, I am a man: yea, if one should clothe with voice the sun, and it teaching the property of its nature should say, I hasting around the circuit of the heaven, let forth bright light to those on the earth:----one would not reasonably suppose, that it were witnessing to itself things not its, but what it really was by nature. In the same way (I deem) as to our Saviour Christ too, even though He says that He is the Light, He will say the truth, and will be found boasting not less than they in things external to Him.
The many therefore living in ill-instructedness, not understanding Emmanuel, suppose that He is vain-glorious and attack Him as though one of us, and have not shuddered to say, Thy record is not true, to Him Who cannot lie, for guile was not found in His Mouth, as it is written. But it behoved Him to lead by the hand them who were astray, having fallen away exceedingly from the truth, and gone away from right reasoning, and in all forbearance to tell them that they had missed of what was becoming, unholily ascribing the love of even lying to Him Who is from above and begotten of God the Father. For true (He says) is My record, even though I hear record of Myself. For in men is sometimes seen the desire from self-love of witnessing things most excellent to themselves, even though they have them not (for prone to ill is their nature); but to Me (He says) belongs not the power of being sick of the same ills as those on the earth. For I know whence I am, Light of Light and Very God of Very God the Father, having the Nature that is beyond the reach of infirmity. For even though (He says) I became Man because of My Love for men, yet not on this account shall I be deemed bereft of God-befitting Dignity, but I remain what I am by Nature, God. A clear proof of this, is My knowing whither I go: for I shall ascend unto the heavens to the Father of Whom I am. This I suppose one would say pertained not to a man as we are, but to Him Who is by Nature God even though He became Man. Hence the words I know whence I am, indicates that the Son is by Nature of the Father, and the whither I go, a demonstration of God-befitting Authority (for He will ascend as God, above the heavens, as Paul saith); yet hath it some fit threat, even if not altogether clear, against the impiety of the Jews. For that He shall full soon depart altogether from their race, does He here evidently say; and leaving them in dearth of the Divine Light, will prepare them for being in ignorance and deep darkness, as He shews them elsewhere more clearly: for He says, While ye have the Light, walk in the light lest darkness come upon you.