On this day Israel’s high priest offered sacrifices as a sin covering for himself, for the other Levites, and for the people. It was also a time for cleansing the tabernacle or the later temples from the polluting effects of sin.

On only one day a year, on the Atonement Day, was the high priest permitted to enter the Most Holy compartment of the tabernacle or of the temple. (Heb 9:7; Le 16:2, 12, 14, 15)

Moses’ brother Aaron was Israel’s high priest when this observance was instituted in the wilderness of the Sinai Peninsula in the 16th century B.C.E. What he was instructed to do furnished the pattern for later observances of the Atonement Day. Visualizing the impressive events of the day makes possible a better understanding of what it meant to the Israelites. Undoubtedly they were then moved to greater consciousness of their sinfulness and the need of redemption as well as to a fuller appreciation of Jehovah’s abundant mercy in making this arrangement to cover their sins of the past year.

Features of the Atonement Day. Aaron was to come into the holy place with a young bull for a sin offering and a ram for a burnt offering. (Le 16:3) On the Atonement Day he set aside his regular priestly garb, bathed in water, and dressed himself in holy linen garments. (Le 16:4) Lots were next drawn by the high priest over two goats (male kids) that were exactly alike in their sound and unblemished condition, these having been obtained from the assembly of the sons of Israel. (Le 16:5, 7) The high priest drew lots over them to determine which of the two would be sacrificed to Jehovah as a sin offering and which would be released in the wilderness, bearing their sins as the ‘goat for Azazel.’ (Le 16:8, 9; compare 14:1-7; see AZAZEL.) He then sacrificed the young bull as a sin offering for himself and his house, which included the entire tribe of Levi, of which his household was a part. (Le 16:6, 11) He thereafter took perfumed incense and the fire holder full of burning coals from off the altar and went inside the curtain, entering the Most Holy. The incense was burned in this innermost room, where the ark of the testimony was located, the cloud of the burning incense overspreading the golden Ark cover on which were two cherubs fashioned in gold. (Le 16:12, 13; Ex 25:17-22) This act paved the way for Aaron afterward to reenter the Most Holy safely.

Aaron, returning from the Most Holy, obtained some of the bull’s blood, entered this compartment with it, and spattered some of the blood with his finger seven times in front of the Ark cover on the E side. Thus was completed the atonement for the priesthood, which rendered the priests clean and able to mediate between Jehovah and his people.​—Le 16:14.

The goat on which the lot fell “for Jehovah” was sacrificed as a sin offering for the people. (Le 16:8-10) The high priest then took the blood of the goat for Jehovah into the Most Holy, using it there to make atonement for the 12 nonpriestly tribes of Israel. In a manner similar to the handling of the bull’s blood, the blood of the goat was sprinkled “toward the cover and before the cover” of the Ark.​—Le 16:15.

By these means Aaron also made atonement for the holy place and the tent of meeting. Then, taking some of the blood of the bull and of the ‘goat for Jehovah,’ he made atonement for the altar of burnt offering, putting some of such blood upon the horns of the altar. He was also to “spatter some of the blood upon it with his finger seven times and cleanse it and sanctify it from the uncleannesses of the sons of Israel.”​—Le 16:16-20.

The high priest now turned his attention to the remaining goat, the one for Azazel. He laid his hands upon its head, confessed over it “all the errors of the sons of Israel and all their revolts in all their sins,” put these upon its head, and then sent it away “by the hand of a ready man into the wilderness.” Thus, the goat carried the errors of the Israelites into the wilderness, where it disappeared. (Le 16:20-22) Thereafter the man who led the goat away had to wash his garments and bathe his flesh in water before reentering the camp.​—Le 16:26.

Aaron now came into the tent of meeting, stripped off the linen garments, bathed, and put on his usual attire. He next rendered up his burnt offering and the people’s burnt offering (using the rams mentioned in Le 16:3, 5) and made atonement, and he made the fat of the sin offering smoke upon the altar. (Le 16:23-25)