He said to me: the speaker is the angel who came to John in 21.9 (see 21.15; 22.1).
These words are trustworthy and true: see 21.5. The reference here is probably to the whole book, so one may translate “All these words are…,” or even “All the words that you have heard are….”
And the Lord, the God of the spirits of the prophets: some take this sentence to be the words of the author, not the angel. There is no translation, however, that separates this from the first sentence in this verse. The meaning is that God inspires the spirits of his prophets. This may be translated “And the Lord God, who inspires the prophets” (so Translator’s New Testament, New Jerusalem Bible, Revised English Bible) or, as Good News Translation has it, “the Lord God, who gives his Spirit to the prophets.” This statement is related to the one in 19.10. The meaning here is that Christian prophets (see 10.7) are inspired, or controlled, by the Holy Spirit as they proclaim their messages. The Revised Standard Version rendering, the Lord, the God of …, follows the punctuation of the Greek text; most translations, however, are like Good News Translation “the Lord God,” and it is recommended that translators follow this rendering. For prophets see 10.7. Another way to render this phrase is “For God, who causes his Spirit to empower those who preach his message….”
Has sent his angel to show his servants what must soon take place: see 1.1. There the text says that he sent his angel to John. This may be implied here, but it is better not to add this to the text. As in 1.1, this is a reference to all the visions and revelations in the book. Show his servants may be expressed as “to make known to all those who serve him” or “to cause all those who serve him to see.”
His servants: either the prophets (see 10.7; 11.18) or else all believers (see 2.20; 7.3; 19.5; 22.3). The latter is preferable.
Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .