When the priests were on assignment at the sanctuary, their duties included the slaughtering of sacrifices brought by the people, sprinkling the blood on the altar, cutting up the sacrifices, keeping the altar fire burning, cooking the meat, and accepting all other offerings, such as the grain offerings. They were to take care of matters dealing with uncleannesses contracted by individuals, as well as their special vows, and so forth. (Le chaps 1-7; 12:6; chaps 13-15; Nu 6:1-21; Lu 2:22-24) They took care of the morning and evening burnt offerings and all other sacrifices regularly made at the sanctuary except those that it was the high priest’s duty to offer; they burned incense on the golden altar. (Ex 29:38-42; Nu 28:1-10; 2Ch 13:10, 11) They trimmed the lamps and kept them supplied with oil (Ex 27:20, 21) and took care of the holy oil and the incense. (Nu 4:16) They blessed the people at the solemn assemblies in the manner outlined at Numbers 6:22-27. But no other priest could be in the sanctuary when the high priest went into the Most Holy to make atonement.​—Le 16:17.

How were the assignments of temple service for the priests in Israel determined?

Of the 24 divisions, or courses, of the priests established by King David, 16 were made up from the house of Eleazar and 8 from the house of Ithamar. (1Ch 24:1-19) However, at least initially, priests from only four of the divisions returned from the Babylonian exile. (Ezr 2:36-39) Some suggest that, in order to continue the former organizational arrangement, the four families returning were divided so that there were again 24 courses. Alfred Edersheim, in The Temple (1874, p. 63), suggests that this was accomplished by each family’s drawing five lots for those who had not returned, thereby forming from their groups 20 more courses to which they gave the original names. John the Baptizer’s father Zechariah was a priest of the eighth division, that of Abijah. However, if the above view represents the true case, he may not have been a descendant of Abijah​—he may have merely belonged to the division which carried his name. (1Ch 24:10; Lu 1:5) Absence of full information does not allow for firm conclusions on these points.

In the temple service the priests were organized under various officers. Lots were drawn in assigning certain services. Each of the 24 divisions served one week at a time, being on assigned duty twice a year. Evidently the entire priesthood served at festival seasons when thousands of sacrifices were offered by the people, as they did at the temple dedication. (1Ch 24:1-18, 31; 2Ch 5:11; compare 2Ch 29:31-35; 30:23-25; 35:10-19.) A priest might serve at other times as long as he did not interfere with the allotted services of the priests on assigned duty. According to rabbinic traditions, in the time of Jesus’ earthly life, the priests were numerous, so that the service of the week was subdivided among the various families making up the division, each family serving one or more days according to their number.

Probably considered the most honorable of the daily services was the burning of incense on the golden altar. This was done after the sacrifice was offered. During the burning of incense, the people would be gathered outside the sanctuary in prayer. Rabbinic tradition is that lots were drawn for this service but that one who had previously officiated was not allowed to participate unless all present had performed the service before. (The Temple, pp. 135, 137, 138) If this is so, a priest would usually have the honor only once in a lifetime. It was this service that Zechariah was performing when the angel Gabriel appeared to him to announce that Zechariah and his wife Elizabeth would have a son. When Zechariah came out of the sanctuary, the crowd gathered there could discern by his appearance and his inability to speak that Zechariah had seen a supernatural sight in the sanctuary; thus the event became public knowledge.​—Lu 1:8-23.

Each Sabbath day, it appears, the priests had the privilege of changing the showbread. It was also on the Sabbath that the priestly division for that week completed its service and the new course began duty for the following week. These and other necessary duties were performed by the priests without constituting a breaking of the Sabbath.​—Mt 12:2-5; compare 1Sa 21:6; 2Ki 11:5-7; 2Ch 23:8.