Moses' instruction to Aaron is a significant aspect of the biblical narrative, particularly in the context of the establishment of the priesthood and the execution of God's commandments. Aaron, the brother of Moses, was appointed by God as the first high priest of Israel, and his role was crucial in the religious and communal life of the Israelites.

The Appointment of Aaron

Aaron's appointment as high priest is first mentioned in the Book of Exodus. God commands Moses to bring Aaron and his sons to serve as priests (Exodus 28:1). This appointment is part of the broader divine plan to establish a system of worship and sacrifice that would set the Israelites apart as God's chosen people.

Instructions for the Priesthood

Moses, acting as God's prophet and leader of Israel, provides Aaron with detailed instructions regarding his duties as high priest. These instructions are primarily found in the books of Exodus, Leviticus, and Numbers. They include guidelines for offerings, sacrifices, and the maintenance of the Tabernacle.

1. Garments and Consecration: In Exodus 28 and 29, Moses is instructed to make holy garments for Aaron, signifying his sacred role. The consecration ceremony, detailed in Exodus 29, involves sacrifices and anointing, symbolizing Aaron's sanctification for service.

2. Sacrificial System: Leviticus chapters 1-7 outline the various offerings Aaron and his sons are to perform, including burnt offerings, grain offerings, peace offerings, sin offerings, and guilt offerings. These sacrifices are central to maintaining the covenant relationship between God and Israel.

3. Day of Atonement: Leviticus 16 provides specific instructions for Aaron on the Day of Atonement, a critical annual event for the atonement of the sins of the people. Aaron is to enter the Most Holy Place with the blood of a bull and a goat, making atonement for himself and the people.

4. Holiness and Conduct: In Leviticus 10, following the tragic deaths of Aaron's sons Nadab and Abihu for offering unauthorized fire, Moses instructs Aaron on the importance of distinguishing between the holy and the common, and between the clean and the unclean (Leviticus 10:10-11).

5. Leadership and Intercession: Aaron's role extends beyond ritual duties. In Numbers 16, during the rebellion of Korah, Moses instructs Aaron to take his censer and make atonement for the people, demonstrating his role as an intercessor (Numbers 16:46-48).

Aaron's Obedience and Challenges

Throughout his service, Aaron faces challenges and moments of failure. Notably, in Exodus 32, Aaron succumbs to the people's demands and fashions a golden calf, an act of disobedience that incurs God's wrath. Despite this, Aaron's role is reaffirmed, and he continues to serve faithfully under Moses' guidance.

Legacy of Aaron's Priesthood

Aaron's priesthood establishes a hereditary line, with his descendants serving as priests in Israel. This lineage is a central element of Israelite worship and is referenced throughout the Old Testament. The instructions given by Moses to Aaron lay the foundation for the Levitical priesthood, which plays a vital role in the spiritual life of Israel.

In summary, Moses' instruction to Aaron encompasses a comprehensive set of guidelines for worship, sacrifice, and priestly conduct, reflecting the holiness and order that God requires from His people. These instructions underscore the importance of obedience, sanctity, and intercession in the life of the high priest and the community he serves.