The high priest must bring purification sacrifices (in older translations called “sin sacrifices”) and reparation sacrifices because of his own weakness. The offence has affected communion with God. The guilt must be removed. That is why the high priest must make sacrifices if the communion with God is to continue. This constant duty keeps the unity of the high priest with his fellow men alive.1
3 Because of this he is obligated to offer sacrifice for his own sins just as he does for those of the people.