Numbers 3:38-40

New Revised Standard Version, Anglicised

³⁸ Those who were to camp in front of the tabernacle on the east—in front of the tent of meeting towards the east—were Moses and Aaron and Aaron’s sons, having charge of the rites within the sanctuary, whatever had to be done for the Israelites; and any outsider who came near was to be put to death. ³⁹ The total enrolment of the Levites whom Moses and Aaron enrolled at the commandment of the Lord, by their clans, all the males from a month old and upwards, was twenty-two thousand.

The Redemption of the Firstborn

⁴⁰ Then the Lord said to Moses: Enrol all the firstborn males of the Israelites, from a month old and upwards, and count their names.