The Greek word behind the word “man” is plural, agreeing with the pronoun “them” later in this verse. The reference is to humanity, yet not to all humanity. For John earlier recorded the heavenly instruction to “come out of [Babylon], my people” (Revelation 18:4) and then went on to explain the demise of Babylon (Revelation 18:8–10, Revelation 18:21) and the destination of all who defied God (Revelation 20:15). The people referred to in the present passage are those who escaped the judgment meted out on the ungodly, those whose names were written in the book of life (Revelation 20:12), and so the new, real humanity.
3 And I heard a loud voice from the throne saying, “Behold, the dwelling place of God is with man. He will dwell with them, and they will be his people, and God himself will be with them as their God.