For no such prophecy was ever brought forth by the will of man, but men spoke from God as they were carried along by the Holy Spirit.
But holy men of God spake as they were moved by the Holy Ghost. They did not of themselves, or according to their own will, foolishly deliver their own inventions. The meaning is, that the beginning of right knowledge is to give that credit to the holy prophets which is due to God.
The Old Testament stands as sure prophecy of Christ's power and coming, confirmed by the Spirit's direction upon those who wrote it. The New Testament is the history fulfilling what the Old foretold; their perfect agreement proves both true. Attend to this lamp shining in darkness until the day dawns.
AI summary
Commenting on 2 Peter 1:19-21
For the prophecy,.... The whole Scripture, all the prophetic writings; so the Jews call the Scriptures "the prophecy" (g), by way of eminence, and from the subject matter of the sacred word: came not in old time by the will of man; was not brought into the world at first, or in any period of time, as and when man would, according to his pleasure...