A.T. Robertson Commentary Revelation 22:6

"And he said unto me, These words are faithful and true: and the Lord, the God of the spirits of the prophets, sent his angels to show unto his servants the things which must shortly come to pass." — Revelation 22:6 (ASV)

He said unto me (ειπεν μο). Apparently the same angel as in 22:1 (21:9,15).

These words (ουτο ο λογο). The same words used in 21:5 by the angel there. Whatever the application there, here the angel seems to endorse as "faithful and true" (πιστο κα αληθινο) not merely the preceding vision (21:9-22:5), but the revelations of the entire book. The language added proves this: "Sent his angel to shew unto his servants the things which must shortly come to pass" (απεστειλεν τον αγγελον αυτου δειξα τοις δουλοις αυτου α δε γενεσθα εν ταχε), a direct reference to 1:1 concerning the purpose of Christ's revelation to John in this book. For "the God of the spirits of the prophets" (ο θεος των πνευματων των προφητων) see 19:10; 1 Corinthians 14:32. Probably the prophets' own spirits enlightened by the Holy Spirit (10:7; 11:8; 22:9).