According to Moses, who is believed to have written Leviticus, the priest had to sacrifice a goat to clean away the people's bad actions, and use its blood as a way to say sorry to God, like wiping away mistakes. This showed the people that doing wrong things comes with a big cost, but God is ready to forgive them if they are truly sorry.
Leviticus 16:15: Then shall he kill the goat of the sin offering, that [is] for the people, and bring his blood within the vail, and do with that blood as he did with the blood of the bullock, and sprinkle it upon the mercy seat, and before the mercy seat:
This verse states that it is not possible for the blood of bulls and goats to take away sins, which contradicts Leviticus 16:15 where the blood of the goat is used for atonement.
Hebrews 10:4: For [it is] not possible that the blood of bulls and of goats should take away sins.