II Pet. 1:16-21
If anyone doubted Peter’s message or his authority to write the admonitions in his letter, he stated some of his qualifications. He had seen with his own eyes the majesty of the Lord Jesus Christ while following Him during His earthly ministry. Peter, along with James and John on the “mount of transfiguration” had heard with his own ears the endorsement of God that Christ was indeed His Son.
The things that Peter had seen and heard confirmed the words of the Old Testament prophets who spoke and wrote only those things that were revealed to them by the Holy Spirit—not their own predictions.