Jamieson, Fausset and Brown on Revelation 5:13

13. The universal chorus of creation, including the outermost circles as well as the inner (of saints and angels), winds up the doxology. The full accomplishment of this is to be when Christ takes His great power and reigns visibly.

every creature--"all His works in all places of His dominion" (Psa 103:22).

under the earth--the departed spirits in Hades.

such as are--So B and Vulgate. But A omits this.

in the sea--Greek, "upon the sea": the sea animals which are regarded as being on the surface [Alford].

all that are in them--So Vulgate reads. A omits "all (things)" here (Greek, "panta"), and reads, "I heard all (Greek, "pantas") saying": implying the harmonious concert of all in the four quarters of the universe.

Blessing, &c.--Greek, "the blessing, the honor, and the glory, and the might to the ages of the ages." The fourfold ascription indicates world-wide universality.