Jamieson, Fausset and Brown on Revelation 8:4

4. the smoke ... which came with the prayers ... ascended up--rather, "the smoke of the incense FOR (or 'given TO': 'given' being understood from Re 8:3) the prayers of the saints ascended up, out of the angel's hand, in the presence of Gods" The angel merely burns the incense given him by Christ the High Priest, so that its smoke blends with the ascending prayers of the saints. The saints themselves are priests; and the angels in this priestly ministration are but their fellow servants (Re 19:10).