II Peter 1:20-21 is well known to many Christians but in it's cultural context it says so much more than meets the eye.
The apostle Peter wrote a passage famous to Bible believing folks about the self-interpreting scripture. However, unless one applies the cultural background, the real message gets lost and the passage becomes a generic message, applied as modern gentiles see fit, out of it's true context.
II Peter 2:16-21 [ESV]
For we did not follow cleverly devised myths when we made known to you the power and coming of our Lord Jesus Christ, but we were eyewitnesses of his majesty. ["eye witnesses of God's majesty" is the Pharisee claim in the legend of their origins]
Their legend says they memorized the words of Jehovah when HE spoke audibly from Mt. Sinai (oral Torah). They claim those words were the divine interpretation of the the Laws of Moses. Therefore, how to interpret Moses (Torah) became their exclusive domain and none dare contradict them, not even The Messiah! This legend was handed down through the generations of Pharisees. It is still a required belief to become a modern Jewish Rabbi.
For when he received honor and glory from God the Father, and the voice was borne to him by the Majestic Glory, This is my beloved Son, with whom I am well pleased, we ourselves heard this very voice borne from heaven, for we were with him on the holy mountain. [This is an undercutting comment about the Pharisees.]
This is a direct refutation of the Pharisee tradition of oral Word of God and their authority. Peter and the apostles also heard audibly directly from heaven the very words from God. That placed them in current times in the same tradition as the Pharisees' claim but more authoritative since it was more recent. That word they heard was Jehovah's confirmation of Jesus as HIS son and that all should listen to him also contradicting the Pharisees.
And we have something more sure, the prophetic word, to which you will do well to pay attention as to a lamp shining in a dark place, until the day dawns and the morning star rises in your hearts,
Their own experience, which was relatively recent and superseded the Pharisees is also less authoritative than something else. What would that be?
knowing this first of all, that no prophecy of Scripture comes from someone's own interpretation [read Pharisees]. For no prophecy was ever produced by the will of man, but men spoke from God as they were carried along by the Holy Spirit.
The Hebrew prophets, their written documents, that's what! Holy men from [of] God, wrote by the influence and direction of the power and presence of God. The Pharisees were not inspired by the power and presence of God in their interpretations. Their teachings were all senses and academic, not inspired. That's why the written word supersedes all oral word and academic interpretations. But Peter was applying this to the Hebrew Bible (Old Testament) only, at that time. Then Peter brings the falsehood of the old Pharisee legends up to date saying that the same thing is happening now with the same false prophets, the Pharisees.
Further, all of the Hebrew prophets who came after Moses were equally inspired. But there is no mention nor even a Pharisee tradition nor legend of any prophet being a Pharisee! They have had no intervention of God's power and presence since Sinai! By their own traditions, there has never been a divinely inspired Pharisee!
II Peter 2:1-3 [ESV]
But false prophets also arose among the people [ref: Pharisee legend of their origins], just as there will be false teachers among you [current believing Pharisees], who will secretly bring in destructive heresies [adherence to the Law and Tradition], even denying the Master who bought them [unbelieving Pharisees], bringing upon themselves swift destruction [*Hebrew worldview].
If you turn your back on Jehovah, He will not bless and protect you. In a metaphor, people live in a sea of evil but a lifeboat is offered by Jehovah to those who honor and worship Him only. But if you punch holes in the boat, the evil sea will inundate your boat and overcome you. That is how destruction comes in a the Hebrew view, men are their own undoing by their own devices when they dishonor and do not respect Jehovah in all they say and do.