The priests in the family line of Aaron were separated into groups. The groups were separated according to the sons of Aaron. The sons of Aaron were Nadab, Abihu, Eleazar and Ithamar.
“Have your brother Aaron brought to you from among the Israelites. His sons Nadab, Abihu, Eleazar and Ithamar must also be brought. They will serve me as priests.
Nadab and Abihu were two of Aaron’s sons. They got their shallow cups for burning incense. They put fire in them. They added incense to it. They made an offering to the Lord by using fire that wasn’t allowed. They did it against his command.
Moses spoke to Aaron and to Eleazar and Ithamar. They were Aaron’s two remaining sons. Moses said, “Take the grain offering left over from the food offerings presented to the Lord. It is very holy. Make bread without yeast from it. Eat it beside the altar.