Jamieson, Fausset and Brown on Revelation 15:7

7. one of the four beasts--Greek, "living creatures." The presentation of the vials to the angels by one of the living creatures implies the ministry of the Church as the medium for manifesting to angels the glories of redemption (Ep 3:10).

vials--"bowls"; a broad shallow cup or bowl. The breadth of the vials in their upper part would tend to cause their contents to pour out all at once, implying the overwhelming suddenness of the woes.

full of ... wrath--How sweetly do the vials full of odors, that is, the incense-perfumed prayers of the saints, contrast with these!