Peter here affirms (beginning with verse 16) that the gospel concerning the Christ was confirmed by God Himself. Though such confirmations came on multiple occasions, Peter here directly refers to the transfiguration of Jesus, as recorded in Matthew 17:1-9. Peter was an eyewitness of that event, and affirms that it is a confirmation of the fact that the messianic prophecies of the Old Testament are realized in Jesus of Nazareth.
At this point he makes a greater application. All scripture is derived from God. The Bible does not have its origin with men. It is not a product of any man’s will, but has its genesis with God (cf. 2 Timothy 3:16-17). As such, no man has the right to ignore it, nor can he alter it with impunity. Instead, “you do well to heed” (vs. 19). It is described as our illumination in darkness. As the great prophet Jeremiah proclaimed, “O Lord, I know the way of man is not in himself; it is not in man who walks to direct his own steps” (Jeremiah 10:23).
