5:13 Then I heard every creature in heaven and on earth and under the earth and on the sea, and all that is in them, saying:
“To him who sits on the throne and to the Lamb
be praise and honor and glory and power,
for ever and ever!”
Then I heard every creature in heaven and on earth and under the earth and on the sea, and all that is in them,
All creation (Psalm 103:19-22).
Originally, all living creatures were placed under Adam's dominion (Genesis 1:28); were confirmed with Noah (Genesis 9:8-11); BUT because of sin, Romans 8:18-22, we all wait for this moment of redemption (taking the book in Revelation 5).
It is interesting to note that this confession is coming from "created things". Today, we have little understanding how ALL of God's creation is waiting to make this confession. For example, how will a rock give Him glory? how will a chunk of ice bestow honor? how will we do this?
saying:
"To HIM who sits on the THRONE and to the LAMB, be
forever and ever!"
The sound comes from everywhere, even as the whole creation was implored to praise Him -- Psalm 148:7-13.
In this verse, we see how beautifully John blends together the worship of the Father (Revelation 4) and the worship of the Son, Lamb (verses 8-12 this chapter).