Verse 20. "Knowing this first" - Considering this as a first principle, that no prophecy of the Scripture, whether that referred to above, or any other, is of any private interpretation-proceeds from the prophet's own knowledge or invention, or was the offspring of calculation or conjecture. The word epilusiv signifies also impetus, impulse; and probably this is the best sense here; not by the mere private impulse of his own mind.
Verse 21. "For the prophecy came not in old time" - That is, in any former time, by the will of man-by a man's own searching, conjecture, or calculation; but holy men of God-persons separated from the world, and devoted to God's service, spake, moved by the Holy Ghost. So far were they from inventing these prophetic declarations concerning Christ, or any future event, that they were feromenoi, carried away, out of themselves and out of the whole region, as it were, of human knowledge and conjecture, by the Holy Ghost, who, without their knowing any thing of the matter, dictated to them what to speak, and what to write; and so far above their knowledge were the words of the prophecy, that they did not even know the intent of those words, but searched what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow. See 1 Pet. i. 11, 12, and the notes there.
1. As the writer of this epistle asserts that he was on the holy mount with Christ when he was transfigured, he must be either Peter, James, or John, for there was no other person present on that occasion except Moses and Elijah, in their glorious bodies. The epistle was never attributed to James nor John; but the uninterrupted current, where its Divine inspiration was granted, gave it to Peter alone. See the preface.
2. It is not unfrequent for the writers of the New Testament to draw a comparison between the Mosaic and Christian dispensations; and the comparison generally shows that, glorious as the former was, it had no glory in comparison of the glory that excelleth. St. Peter seems to touch here on the same point; the Mosaic dispensation, with all the light of prophecy by which it was illustrated, was only as a lamp shining in a dark place. There is a propriety and delicacy in this image that are not generally noticed: a lamp in the dark gives but a very small portion of light, and only to those who are very near to it; yet it always gives light enough to make itself visible, even at a great distance; though it enlightens not the space between it and the beholder, it is still literally the lamp shining in a dark place. Such was the Mosaic dispensation; it gave a little light to the Jews, but shone not to the Gentile world, any farther than to make itself visible.
This is compared with the Gospel under the emblem of daybreak, and the rising of the sun. When the sun is even eighteen degrees below the horizon daybreak commences, as the rays of light begin then to diffuse themselves in our atmosphere, by which they are reflected upon the earth. By this means a whole hemisphere is enlightened, though but in a partial degree; yet this increasing every moment, as the sun approaches the horizon, prepares for the full manifestation of his resplendent orb: so the ministry of John Baptist, and the initiatory ministry of Christ himself, prepared the primitive believers for his full manifestation on the day of pentecost and afterwards. Here the sun rose in his strength, bringing light, heat, and life to all the inhabitants of the earth. So far, then, as a lantern carried in a dark night differs from and is inferior to the beneficial effects of daybreak, and the full light and heat of a meridian sun; so far was the Mosaic dispensation, in its beneficial effects, inferior to the Christian dispensation.
3. Perhaps there is scarcely any point of view in which we can consider prophecy which is so satisfactory and conclusive as that which is here stated; that is, far from inventing the subject of their own predictions, the ancient prophets did not even know the meaning of what themselves wrote. They were carried beyond themselves by the influence of the Divine Spirit, and after ages were alone to discover the object of the prophecy; and the fulfillment was to be the absolute proof that the prediction was of God, and that it was of no private invention - no discovery made by human sagacity and wisdom, but by the especial revelation of the all-wise God. This is sufficiently evident in all the prophecies which have been already fulfilled, and will be equally so in those yet to be fulfilled; the events will point out the prophecy, and the prophecy will be seen to be fulfilled in that event.