What does 2 Peter 1:17 mean?
Peter's comments here are the beginning of a single sentence which runs through verse 18.The specific event Peter uses as proof, here, is one of the most unique and profound moments in all of the Bible. We commonly call it the "transfiguration" because Peter, James, and John were allowed to see Jesus "transfigured" from His appearance as a normal man into His true and eternal appearance as the Son of God. This is described in more detail in Matthew 17:1–13, Mark 9:2–13, and Luke 9:28–36.
Peter saw Jesus' face shining as the sun. His clothes became as white as light. But the part Peter emphasizes here is hearing the voice of God—the Majestic Glory—speaking, declaring that Jesus is His beloved Son and that He, the Father, is very pleased with Jesus. Peter's argument is that God the Father Himself gave honor and glory to Jesus. And, Peter knew Jesus was the Son of God because he heard God say so.