Numbers Chapter 3 World English Bible
Nadab and Abihu died before Yahweh, when they offered strange fire before Yahweh, in the wilderness of Sinai, and they had no children. Eleazar and Ithamar ministered in the priest's office in the presence of Aaron their father.
for all the firstborn are mine. On the day that I struck down all the firstborn in the land of Egypt I made holy to me all the firstborn in Israel, both man and animal. They shall be mine. I am Yahweh."
Those who encamp before the tabernacle eastward, in front of the Tent of Meeting toward the sunrise, shall be Moses, and Aaron and his sons, keeping the charge of the sanctuary for the charge of the children of Israel. The stranger who comes near shall be put to death.
You shall take the Levites for me (I am Yahweh) instead of all the firstborn among the children of Israel; and the cattle of the Levites instead of all the firstborn among the cattle of the children of Israel."