This was written from Rome in c. 64-66 A.D. during a time of persecution of belivers by Nero.
2 Peter 1:12-15
So I will always remind you of these things, even though you know them and are firmly established in the truth you now have. I think it is right to refresh your memory as long as I live in the tent of this body, because I know that I will soon put it aside, as our Lord Jesus Christ has made clear to me. And I will make every effort to see that after my departure you will always be able to remember these things.
He wants to remind his readers of everything mentioned previously, because he knows he will soon depart- perhaps recalling Jesus words to him in John 21:18. He wants his readers to be able to access what he is writing after he is gone.
John 21:18
Very truly I tell you, when you were younger you dressed yourself and went where you wanted; but when you are old you will stretch out your hands, and someone else will dress you and lead you where you do not want to go.
2 Peter 1:16-18
For we did not follow cleverly devised stories when we told you about the coming of our Lord Jesus Christ in power, but we were eyewitnesses of his majesty. He received honor and glory from God the Father when the voice came to him from the Majestic Glory, saying, “This is my Son, whom I love; with him I am well pleased.” We ourselves heard this voice that came from heaven when we were with him on the sacred mountain.
Peter here is speaking as a witness to the transfiguration in Matthew 17.
2 Peter 1:19
We also have the prophetic message as something completely reliable, and you will do well to pay attention to it, as to a light shining in a dark place, until the day dawns and the morning star rises in your hearts.
Everything God wanted to say, he said through the Old Testament, then through the coming of Jesus.
Hebrews 1:1-2
In the past God spoke to our ancestors through the prophets at many times and in various ways, but in these last days he has spoken to us by his Son, whom he appointed heir of all things, and through whom also he made the universe.
All prophecy in scripture culminates in Jesus Christ After this there is no more. There will be no new revelation as in "another testament" or an add on to the scriptures, so there is no need to seek it out.
Be careful with this because anyone can say, "God told me to tell you - you'll be wealthy" etc. If you listen to a lot of this you could be tempted to start asking people what God said instead of going to God yourself, as Hebrews 4:16 for example encourages us to do.
Hebrews 4:16
Let us then approach God’s throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need.
Another example was King Saul in 1 Samuel 28:17 who visited a medium to bring up Samuel to tell him what to do because God didn't answer him. The result was he and his sons died in battle against the Philistines.
There is also Jeremiah 28:14-16 where Jeremiah told Hananiah that God had not sent him, and he removed from the face of the earth. Also, Acts 20:30 where Paul warns the church to look out for people inside the church who would distort the truth.
Matthew Henry (late 17th, early 18th century) in his commentary says this, in reference to the Old Testament: it is a "more sure word of prophecy," and says what was prophecy in the Old Testament became history in the New Testament.
2 Peter 1:20-21
Above all, you must understand that no prophecy of Scripture came about by the prophet’s own interpretation of things. For prophecy never had its origin in the human will, but prophets, though human, spoke from God as they were carried along by the Holy Spirit.
Prophecy was never the will of man. Peter finishes this section by describing where prophecy came from: men moved by the Holy Spirit. This is Similar to what he said in 1 Peter 4:10-12 describing our salvation, the Spirit of Christ was in them when he told about the suffering of Christ and the glory that would follow.
1 Peter 4:10-12
Each of you should use whatever gift you have received to serve others, as faithful stewards of God’s grace in its various forms. If anyone speaks, they should do so as one who speaks the very words of God. If anyone serves, they should do so with the strength God provides, so that in all things God may be praised through Jesus Christ. To him be the glory and the power for ever and ever. Amen. Dear friends, do not be surprised at the fiery ordeal that has come on you to test you, as though something strange were happening to you.
