Eleazar ... Ithamar

These are the names of Aaron's sons.

Do not let your hair on your heads hang loosely, and do not tear your clothes

Yahweh is telling Aaron and his sons not to show any outward signs of grief or mourning.

"so that you will not die"

"not be angry with all the people of Israel"

"all the people of Israel"

"for those whom Yahweh killed with his fire"