Leviticus 8:2
Take Aaron and his sons with him, and the garments, and the anointing oil, and a bullock for the sin offering, and two rams, and a basket of unleavened bread; Take Aaron and his sons with him, and the garments, and the anointing oil, and a bullock for the sin offering, and two rams, and a basket of unleavened bread;
The verse provides for the sacred consecration of Aaron as high priest. It sets apart Aaron himself for that holy work rather than leaving him in a common standing. It also establishes the priestly office for Aaron's family as a continuing line. That office was conferred by God and honored by Him as His own appointment.