Numbers 3:9-11

Amplified Bible, Classic Edition

⁹ And you shall give the Levites [as servants and helpers] to Aaron and his sons; they are wholly given to him from among the Israelites.

¹⁰ And you shall appoint Aaron and his sons, and they shall observe and attend to their priest’s office; but the excluded [anyone daring to assume priestly duties or privileges who is not of the house of Aaron and called of God] who comes near [the holy things] shall be put to death.

¹¹ And the Lord said to Moses,