After the events with Aaron’s sons, Adonai outlines the regulations for entering the Holy of Holies behind the Holy Curtain in front of the Ark of the Covenant. Aaron was not allowed to come in just any time because Ehyeh Asher Ehyeh appears in the cloud over the kapparah. He was only allowed to enter on Yom Kippur, the day of atoning for the sins of Isra’el, the priesthood, and the Tabernacle; it was a solemn day of fasting.
Have you ever thought about why there needs to be a separation of sheep and goats? I remember the first time I heard that sheep and goats look alike, especially Middle Eastern goats and sheep. I found a fun article about how sheep and goats are similar and how they are different.