Peter knows his death is near, so he is determined to keep believers firmly grounded in truths they already know. The message about Christ’s power and coming is trustworthy because it rests on two united witnesses: apostolic eyewitness testimony to Jesus’ majesty and prophetic Scripture given by God through the Holy Spirit, not invented by man.

Peter is still speaking about the truths he emphasized in the earlier verses—growth in godliness, God’s calling, perseverance, and the promised entrance into Christ’s kingdom. He has not changed subjects. Instead, he explains why he keeps repeating these things. His readers already know them and are established in them, but they still need to be reminded. Peter sees repeated reminder as faithful ministry, not unnecessary repetition.

He says it is right to keep stirring them up as long as he is in this “tent,” meaning his present bodily life. The picture of a tent highlights how temporary this life is. Peter knows his earthly life will soon end because the Lord Jesus Christ has made this known to him, likely echoing what Jesus had told him earlier about his death. So he writes with urgency. He wants to make every effort so that after his “departure”—a respectful way of speaking about death—these believers will continue to remember these truths.

Peter then explains why his message should be trusted. The apostles did not follow cleverly invented stories when they proclaimed the power and coming of the Lord Jesus Christ. This sets apostolic truth in sharp contrast to fabricated claims. Peter is not merely saying Christianity is meaningful. He is saying it is true, grounded in real revelation.

The phrase “power and coming” most naturally refers to Christ’s future return in glory. In that sense, the transfiguration served as a preview of that coming majesty. Peter and the others were not passing on rumors. They were eyewitnesses of Christ’s majesty. On the holy mountain they saw Jesus’ greatness revealed, and they heard the Father publicly honor the Son. The heavenly voice—“This is my dear Son, in whom I am delighted”—reveals who Jesus truly is: the Son approved and honored by the Father. Peter’s testimony, then, rests on what he saw and heard.

Peter next points to the prophetic word. He is not lowering the value of the transfiguration or setting Scripture against apostolic witness. He joins them together. The prophetic Scriptures are fully reliable, and believers do well to pay close attention to them. In this present age, Scripture is like a lamp shining in a dark place. It gives real light now, even though the full brightness is still to come.

That light remains necessary until “the day dawns and the morning star rises in your hearts.” This looks ahead to the future day of Christ’s appearing, when what is now known by faith will be openly revealed. It is best not understood as merely a private mystical experience. It points to the final dawning of Christ’s glory, personally received by believers when that day arrives.

Peter then explains why prophetic Scripture is so dependable. Above all, they must understand that no prophecy of Scripture comes from the prophet’s own source or impulse. The point here is mainly about origin, not mainly a prohibition against ordinary believers reading Scripture for themselves. Verse 21 explains verse 20: prophecy was never produced by human will. Instead, men spoke from God as they were carried along by the Holy Spirit.

That means the prophets were real human speakers, not machines. Yet the source and controlling impulse behind their message was the Holy Spirit. The prophecy of Scripture is trustworthy because it is God-given. Human authors truly spoke, but they spoke from God under the Spirit’s guiding power.

This whole paragraph prepares for Peter’s warning about false teachers in the next chapter. Before exposing their deceptive words, he establishes why his own message should be believed instead. The churches must not judge truth by novelty, personality, or persuasive speech. They must remain anchored to the apostolic witness about Christ and to the written prophetic word God has given.

Key Truths: - Believers need repeated reminder of apostolic truth, even when they already know it. - Peter viewed his coming death as a reason to strengthen the church, not to withdraw from service. - The apostolic message about Christ’s coming is not myth but eyewitness-based revelation. - The transfiguration was a true revelation of Jesus’ majesty and a preview of his future glorious coming. - The Father Himself honored Jesus as His beloved Son. - Scripture is a lamp for the present dark age until Christ is fully revealed. - Biblical prophecy did not arise from human invention, but from men speaking from God as they were carried along by the Holy Spirit.