The Angel of the Book of Revelation
It is not always readily remembered that while Jesus is being quoted in the book of Revelation, John is speaking to what is an Angel -- an angel who is transmitting words from Jesus.
The only time John sees Jesus in person is when John is "raptured" -- taken up into heaven -- to see Jesus seated at the right hand of God.
Until that time, the words of the angel relay Jesus' words, but it is the angel who is present with John on earth:
The revelation from Jesus Christ, which God gave him to show his servants what must soon take place. He made it known by sending his angel to his servant John... (Rev. 1:1 NIV.)
This is explained in the Inter Varsity Press commentary on the Book of Revelation entitled "The Vision and the Angel."
The commentary helps us by synthesizing this important aspect of Revelation:
Another difference is that in the book of Revelation an angel is introduced as an additional link in the chain. The revelation proceeds from God to Jesus Christ through the angel to one servant in particular, named John. The long letter of "John" comprises the remainder of the book.
Who is this angel and, more importantly, who is "John"? The two are seen together near the end of the book. At the end of John's final vision of the new Jerusalem (21:9--22:5), the angel who "showed" him the vision in all its detail (21:9, 10; 22:1) concludes with the solemn assurance, "These words are trustworthy and true" (22:6). This angel is "one of the seven angels who had the seven bowls full of the seven last plagues" (21:9; compare 15:1, 6), which one we are not told. When the angel has finished speaking, another voice adds by way of summary, "`The Lord, the God of the spirits of the prophets, sent his angel to show his servants the things that must soon take place'" (22:6). An angel identified in a similar way (17:1) plays much the same role in a preceding vision of God's judgment on "Babylon the prostitute" (17:1--19:10), concluding with a similar assurance from the angel that "these are the true words of God" (19:9).
Here at the beginning of the book the angel is still unidentified, and he will play no recognizable role in John's early visions. Only in the two later visions will the reader come to know the angel by what he does for John as revealer and interpreter. Yet so important is the angel in John's experience that John twice falls down to worship him (19:10; 22:8) and has to be reminded that the angel is merely a "fellow servant with you and with your brothers the prophets and of all who keep the words of this book. Worship God!" (22:9; compare 19:10). If we are reading the book for the second time, we may sense that the closing scenes of John's visionary experience are still fresh in his mind as he begins to write.