I know that some will dispute what I'm about to write, but here goes ..
Last time we were told to make every effort to build on our faith. This time Peter, who is shortly going to die, says he is going to make every effort. His task now is to make sure that those who follow him will always remember what he taught.
He wants us to know that he didn't make it up. He really knew Jesus. He really saw him in glory on a mountain top. He heard the voice saying, 'This is my Son, whom I love; with him I am well pleased."
A generation later there was a man called Papias, who tells us that Mark's gospel was written by Peter's interpreter from the things that Peter remembered about Jesus. The point is the same: he didn't make it up.
Peter also wants us to know that the scriptures aren't the product of cleverly invented stories; they were inspired by God. As we will see in chapter four, this includes the letters written by the Apostle Paul.
And my job as a pastor is to keep reminding you of these things. Jesus lived. Jesus died. Jesus rose again. His kingdom is coming. not a cleverly invented story but the greatest truth of all.