Leviticus 16-18…The day of atonement and laws regarding purity.
Most of the procedures followed on the Day of Atonement were similar to those followed for the other offerings except that the blood of the sacrifices was sprinkled on the mercy seat in the Most Holy Place as well (Leviticus 16:14). This was done lest the accumulated sin cause God to immediately punish the high priest and the people. Aaron and the later high priests also had to throw incense in the air (vv. 12–13) in front of them as they approached the ark of the covenant so as to keep them from being able to see the Lord; otherwise, they would have died (Ex. 33:12–23).
Besides the sacrifice of a bull on behalf of the priesthood, two goats were brought to the tabernacle/temple to deal with the sin of the entire nation (Lev. 16:6–10). One goat was killed and its blood was sprinkled on the mercy seat (vv. 15–19). This sacrifice on the Day of Atonement resulted in propitiation — the satisfaction of God’s wrath on a substitute in place of the people. The other goat, after hands were laid on it, was sent to Azazel in the wilderness and freed, probably meaning it was taken to a desolate mountain and killed (vv. 20–22). Here it is clear that expiation was accomplished. The sins of the people were taken away from Israel and away from the holy camp.