1Then I saw a new heaven and a new earth,for the first heaven and the first earth had passed away, and the sea was no more.
This paragraph breaks into two parts. It relates a) what John saw (Revelation 21:1–2); b) what John heard (Revelation 21:3–8). What John heard provides the explanation of what he saw.
1 Then I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and the sea was no more.