Behold, I make all things new (Idou kaina poiō panta). The first time since Rev 1:8 that God has been represented as speaking directly, though voices have come out of the throne before (Rev 21:3) and out of the sanctuary (Rev 16:1, Rev 16:17), which may be from God himself, though more likely from one of the angels of the Presence. This message is not addressed to John (Rev 7:14; Rev 17:7; Rev 21:6; Rev 22:6), but to the entire world of the blessed. See Isa 43:18. for the words (Idou egō poiō kaina). The idea of a new heaven and a new earth is in Isa 65:17; Isa 66:22; Psa 102:25. For the locative here with epi (epi tōi thronōi) see Rev 7:10; Rev 19:4 (genitive more usual, Rev 4:9.; Rev 5:1, Rev 5:7, Rev 5:13, etc.). See Rev 20:11 for the picture.
And he saith (kai legei). Probably this means a change of speakers, made plain by moi (to me) in many MSS. An angel apparently (as in Rev 14:13; Rev 19:9.) assures John and urges him to write (grapson as in Rev 1:11; Rev 2:1, Rev 2:8, Rev 2:12, Rev 2:18; Rev 3:1, Rev 3:7, Rev 3:14; Rev 14:3). The reason given (hoti, for) is precisely the saying in Rev 22:6 and he uses the two adjectives (pistoi kai alēthinoi) employed in Rev 19:11 about God himself, and Rev 3:14 about Christ. In Rev 19:9 alēthinoi occurs also about “the words of God” as here. They are reliable and genuine.