2 Peter 1:21 21For no prophecy was ever brought by the will of a person, but people spoke from God as they were brought along by the Holy Spirit.
Verse 21 continues the thought of verse 20 and emphasizes the source of prophecy and not so much the idea of interpretation. The verb brought (from pherō) is used twice in the verse in a sharp comparison about prophecy’s source. True prophecy never came through human thinking but by the Holy Spirit. This same verb is used in verses 17-18 for how the voice “was brought” from heaven. The voice from heaven and the prophetic word had the same source, and Peter was a witness to both. In Jeremiah’s day, there were prophets who claimed that God would rescue Jerusalem from the Babylonians. Jeremiah 28:9 says that the words of the true prophet will come true. Time proved all the prophets who spoke from their own thinking were wrong. Jeremiah, who spoke God’s word, was proven correct.
True prophets speak through the empowerment of the Holy Spirit. The Holy Spirit puts ideas and even specific words into their minds. The Old Testament prophets did not have all the details about Christ but had glimpses into the future (Rom 16:25). Their prophecies and Peter’s eyewitness account prove that the message Peter preached to the readers is true. Anything else must be rejected.