He thought for a second and realized that other people must have done the same thing, and that it was worth going back to look by the side of the road since even if he couldn't find his own gas cap, he might be able to find another one that fit.
Sure enough, after only a short time of searching, he found a gas cap. He carefully wiped it off and slipped it into place with a satisfying click.
He told his wife as he climbed back into the car, "I may have lost my gas cap, but I found another one that fits and it's even a better cap than the one I had — it locks!"
Oops! A locking gas cap is a great idea — but only if you have the key that opens it! Understanding the Bible is much the same way. Remember when Jesus first began speaking in parables — his apostles came to him for an explanation. They wanted the "key," and Jesus gave it to them. Jesus said, "To you it has been given to know the mystery of the kingdom of God" (Mark 4:11).
The book of Revelation is a difficult (some would say impossible) book for people to understand. It becomes a much easier task when you have the "key" explaining the symbolism of the numbers, colors and images found in the book.
Sometimes the ministry of Jesus is referred to as a "mystery." Paul wrote often about the "mystery of the gospel" (Ephesians 6:19), the "mystery of Christ" (Colossians 4:3), or simply "the mystery" (Ephesians 3:9). The word "mystery" means that it was something that was "hidden" for a while. All through the Old Testament, God was preparing for Jesus Christ to come to this earth, but no one fully understood what that would mean. The prophets foretold his coming, but they didn't fully understand (1 Peter 1:10-12). Even the angels didn't know what God had in mind. But we do. We understand the significance of the crucifixion and the resurrection.
[T]he mystery which has been hidden from ages and from generations, but now has been revealed to His saints. To them God willed to make known what are the riches of the glory of this mystery among the Gentiles: which is Christ in you, the hope of glory. (Colossians 1:26-27 NKJV)