Albert Barnes on Revelation 5:14

And the four beasts said, Amen. The voice of universal praise came to them from abroad, and they accorded with it, and ascribed honour to God.

And the four and twenty elders fell down, etc. The living creatures and the elders began the work of praise, (Rev 5:8) and it was proper that it should conclude with them; that is, they give the last and final response.--Professor Stuart. The whole universe, therefore, is sublimely represented as in a state of profound adoration, waiting for the developments to follow on the opening of the mysterious volume. All feel an interest in it; all feel that the secret is with God; all feel that there is but One who can open this volume; and all gather around, in the most reverential posture, awaiting the disclosure of the great mystery.

(e) "four beasts" Rev 19:4