An angel delivered the Book of Revelation to John. This angel, and other angels, are mentioned several times in the Book. We should observe that the angel is described as Jesus’ angel, that although a powerful being, he is only a servant of Jesus. In fact, three different servants of Jesus are mentioned here: there are believers in general, there is John the apostle, and there is the angel. We can be sure that the angel was delighted to perform the task.
Many decades had gone by since John had seen Jesus. He had the privilege of witnessing Jesus ascend to heaven; he could recall how he had used to lean on the breast of Jesus. No doubt, he had often been asked, ‘What was Jesus like?’ John would have done his best to answer that question.
And he may have been asked, ‘What does he look like now?’ Prior to receiving this book, he could have replied, ‘He is great, but I don’t know how to depict him.’ John would not have had to say such a thing again because he was now going to bear testimony to the glory of Jesus. Of course, John may yet ask us, ‘Did you read the book that Jesus gave to me to pass on?’
It is likely that one reason the Book of Revelation was sent to John was because he was the last of the apostles, and he possessed the authority to say if a book belonged to the Word of God. This is what he did, and it is included in our canon of scripture. Because John was an authentic apostle, he wanted to ensure that people understood the book in three ways. First, it was a message from God the Father (the word of God); second, it was a message from and about Jesus Christ (the testimony of Jesus); and third, it was a prophecy, not only focussed on the future, but a message for the people of God in the present.
From his own self-description, we can see that John was a faithful servant of Jesus. He limited his testimony to all that he saw. It is not surprising that later in the book, he warns about adding to or taking from its words. I suppose we can say that he also passed on everything that he saw because he recognised that what was said about Jesus was wonderful, and that it was important for believers to know about his present dignity and glorious intentions as well his past achievements.