The instructions for Aaron, the brother of Moses and the first high priest of Israel, are primarily found in the books of Exodus, Leviticus, and Numbers. These instructions were given by God to establish the priesthood and to ensure that the Israelites had a mediator between themselves and God. Aaron's role was crucial in the religious and ceremonial life of the Israelites, and his duties were detailed with precision to maintain holiness and order in worship.

Appointment and Anointing

Aaron's appointment as high priest is first mentioned in Exodus 28:1, where God commands Moses, "Bring near to you your brother Aaron and his sons with him from among the Israelites to serve Me as priests—Aaron, Nadab and Abihu, Eleazar and Ithamar, Aaron’s sons." This divine selection underscores the importance of the priesthood as a divinely instituted office.

The anointing of Aaron is described in Exodus 29 and Leviticus 8. In Exodus 29:7, God instructs, "Take the anointing oil and anoint him by pouring it on his head." This anointing symbolized Aaron's consecration and the sanctity required for his service.

Priestly Garments

The garments of the high priest were designed to reflect the glory and beauty of the office. Detailed instructions for these garments are found in Exodus 28. The ephod, breastplate, robe, tunic, turban, and sash were to be made with specific materials and colors. Exodus 28:2 states, "Make holy garments for your brother Aaron, to give him glory and splendor." These garments were not only for aesthetic purposes but also served as a constant reminder of the high priest's sacred duties.

Duties and Responsibilities

Aaron's primary responsibilities included offering sacrifices, maintaining the sanctuary, and interceding for the people. Leviticus 16 outlines the Day of Atonement, a significant annual event where Aaron was to enter the Most Holy Place to make atonement for himself and the people. Leviticus 16:34 states, "This shall be a permanent statute for you, to make atonement for the Israelites once a year because of all their sins."

Aaron was also responsible for maintaining the lampstand, burning incense, and ensuring the showbread was in place (Exodus 30:7-8, Leviticus 24:5-9). These daily and weekly rituals were essential for the ongoing worship and spiritual life of the nation.

Conduct and Holiness

The holiness required of Aaron and his sons is emphasized throughout the instructions. Leviticus 10 recounts the tragic incident of Nadab and Abihu, Aaron's sons, who offered unauthorized fire before the Lord and were consumed by fire as a result. This event underscores the seriousness of adhering to God's commands. Leviticus 10:3 records God's words: "Among those who approach Me, I will be proved holy; in the sight of all the people, I will be honored."

Prohibitions and Restrictions

Specific prohibitions were placed on Aaron and his descendants to maintain their purity and distinctiveness. Leviticus 21 outlines various restrictions, including prohibitions against contact with the dead (except for close relatives) and marrying certain women. These laws were designed to keep the priesthood undefiled and set apart for God's service.

Legacy and Succession

Aaron's legacy as the first high priest set a precedent for the Levitical priesthood. His descendants continued to serve in this capacity, with Eleazar, his son, succeeding him (Numbers 20:25-28). The priesthood established through Aaron remained a central element of Israelite worship until the destruction of the Second Temple.

The instructions for Aaron highlight the importance of obedience, holiness, and the mediatorial role of the priesthood in the Old Testament, foreshadowing the ultimate High Priest, Jesus Christ, who would fulfill and surpass the Aaronic priesthood.