'Office' in the Bible

These are the names of the sons of Aaron, the priests who were anointed, whom Aaron consecrated and ordained to minister in the priest’s office.

But Nadab and Abihu died in the presence of the Lord when they offered strange (unholy, unacceptable, inappropriate) fire before the Lord in the Wilderness of Sinai; and they had no sons. So Eleazar and Ithamar served as priests in the presence and under the supervision of Aaron their father.

So you shall appoint Aaron and his sons, and they shall observe and attend to their priesthood; but the layman (non-Levite) who approaches [the holy things] shall be put to death.”