And another angel came and stood at the altar, having a golden censer. And much incense was given unto him to give with the prayers of the saints at the golden altar before the throne. And the smoke of the incense with the prayers of the saints went up before God out of the hand of the angel. (Revelation 8:3-4)

Commentary
He calls the altar a censer, as being receptive of incense. When Christ appears, the prayers of the saints, like some first-fruit and honored, primal offering, are brought to Him by our guardian angels, prayers which are naturally sweet-smelling, but which become sweeter-smelling with the cooperation of the holy angels. That is why it is said, much incense was given unto him; it was clearly God's gift to the angels to protect human beings and to make their prayers acceptable.

Oecumenius (6th C), Commentary on the Apocalypse, page 83
Fathers of the Church, Vol. 112
Catholic University of America