Moses served as God's minister in setting the Aaronic priesthood into motion. He came before the Lord with his brother and his nephews, with the anointing oil, with a young bull, with two rams, with unleavened bread and with the people of Israel. He obeyed God's command by ceremoniously washing Aaron and his sons, by clothing them with all of the garments appointed for their office, by anointing the holy things and Aaron with oil, by slaying the sin offering and carrying out the proper rituals attached to it, by slaying the burnt offering and fulfilling the assigned rites connected to it, by anointing Aaron and his sons with the blood and by commanding them in accordance with what God had instructed.
Aaron and his sons did as Moses commanded. They boiled the meat from the other ram and ate of it. And, they remained in continual service in the tabernacle for the next week. The Aaronic priesthood and all that it represented was in place. Of course, it was a temporary arrangement. A greater order was actually already in place (Hebrews 7:6, 9 & 10). Our high priest ministers according to the rituals of a higher priesthood. For Christ, the commencement of His priesthood marked the completion of it. He sat down at the right hand of the Father on high, never to be needed again to make an atoning sacrifice (Hebrews 10:10).