The part assigned to each priest in his week of service was decided by lot. Three were employed at the offering of incense—to remove the ashes of the former service; to bring in and place on the golden altar the pan filled with hot burning coals taken from the altar of burnt offering; and to sprinkle the incense on the hot coals; and, while the smoke of it ascended, to make intercession for the people. This was the most distinguished part of the service (Rev 8:3), and this was what fell to the lot of Zacharias at this time [Lightfoot].
Jamieson, Robert, A. R. Fausset, and David Brown. Commentary Critical and Explanatory on the Whole Bible. Oak Harbor, WA: Logos Research Systems, Inc., 1997. Print.