An emission of fluid from the body, whether regular like semen or menstruation or irregular, makes you unclean. Regular emissions required washing and being unclean until evening. In addition to that, irregular emissions required a washing 7 days later and a sacrifice on the 8th day.
Instructions for the day of atonement, the only day the priest entered the holy of holies. A bull and ram for sin offering, with their blood sprinkled before the ark. Then another goat to be a scapegoat, released into the wilderness with the sins of Israel laid on it. This is a day for all Israel to afflict their souls - atonement is made for you.
How this is about Jesus
Not with the blood of bulls and goats, but with His own precious blood, Jesus entered the holy of holies and paid for our sins. If God made that blood effective for purification, how much more has He made the blood of His Son effective to cleanse our soul and conscience? (Hebrews 9:13-14)
All the washing of the priests in the last few chapters points to Jesus' baptism, done to fulfill all righteousness. The priest was to wash before beginning his ministry of offering sacrifice for Israel.
We need to think of our defilement and atonement in this modern world. Our sin requires acts of repentance and reconciliation. We must lay our sins on Jesus, and trust God to atone for those sins with His blood.