Aaron needed to offer a bull for himself before entering the Holy of Holies because he, like all men, was a sinner and needed atonement before he could approach the presence of God. The bull was a sin offering for the high priest to cleanse him from personal guilt so he could intercede for the people without bringing judgment upon himself.
Leviticus 16:6 says:
“Aaron shall offer the bull as a sin offering, which is for himself, and make atonement for himself and for his house.”
Even though Aaron was the high priest, he was not exempt from sin. Before he could represent Israel, he had to deal with his own defilement. Entering the Holy of Holies without proper atonement would result in death, as God’s presence is holy and cannot be approached by the unclean.
Hebrews 5:3 reflects on this requirement:
“Because of this he is required as for the people, so also for himself, to offer sacrifices for sins.”
This pointed forward to the superiority of Christ’s priesthood. Unlike Aaron, Jesus had no sin of His own to atone for. Hebrews 7:27 says:
“Who does not need daily, as those high priests, to offer up sacrifices, first for His own sins and then for the people’s, for this He did once for all when He offered up Himself.”
Aaron’s need to offer a bull for his own sins before entering the Holy of Holies underscored the holiness of God, the sinfulness of man, and the necessity of a perfect high priest to mediate between the two.
