Having every one of them harps, and golden vials,— Harps were a principal part of the temple music: vials were also of common use in the temple service; but they were not like those small bottles which we now call vials, but like cups, or little bowls, on a plate, in allusion to the censers of God in which the priests offered incense in the temple. These censers were a sort of cups, which, because of the heat of the fire burning the incense, were often put upon a plate or saucer, something resembling a tea-cup and saucers. To offer incense to God, or before his presence in the temple, was an act of honour and religious worship peculiar to the priest's office; and the prayers of the church are often compared to it. See Psalms 141:2. So that these expressions well represent the whole heavenly church of saints and angels offering a very high act of religious worship and adoration unto Christ. Some read here, golden bowls full of perfumes.
Related Commentaries of Revelation 5:8
Revelation 5:8
8 And when he had taken the book, the four beasts and four and twenty elders fell down before the Lamb, having every one of them harps, and golden vials full of odours,a which are the prayers of saints.