In 2 Peter 1:16-19, Peter is emphasizing the reliability of the message he and other apostles were sharing about the coming of Jesus Christ. He contrasts their testimony with "cleverly devised stories," meaning myths or fabrications. He states that their message is not based on human imagination, but rather on their firsthand experience as eyewitnesses to the majesty of Jesus.
Peter recalls the event of the Transfiguration, where Jesus was revealed in his divine glory before Peter, James, and John on a mountain. During this event, a voice from heaven affirmed Jesus as the beloved Son of God. Peter himself heard this voice, and he wants to assure his readers that their message is grounded in these concrete experiences.
Furthermore, Peter underscores the importance of the prophetic word, referring to the Old Testament prophecies that pointed to the coming of Christ. He encourages his readers to pay attention to these prophecies, likening them to a "light shining in a dark place." This imagery suggests that the prophetic word provides guidance and understanding in a spiritually dark world.
In essence, Peter's message in these verses is about the reliability of the apostles' testimony regarding Jesus' divinity and the importance of the prophetic word as a guiding light for believers. He wants his readers to understand that the foundation of their faith is rooted in genuine experiences and the fulfillment of prophecies.