1. Leviticus 16:3 (ESV)
  2. Exposition

What offerings does God require of the High Priest?

Leviticus 16:3 (ESV)

3 But in this way Aaron shall come into the Holy Place: with a bull from the herd for a sin offering and a ram for a burnt offering.

The priest could only enter the Temple with a young bull for purification for himself and a ram as a burnt offering to make atonement.