Aaron and his sons are now dedicated to conduct their sacred services to God. In this Parashat, Shemini, two of Aaron's sons, Nadav and Avihu, enter the Tent of Meeting and apparently offer a "strange fire" to God.
"And the sons of Aaron, Nadav and Avihu, took each person his censer and placed fire in them and laid incense thereon and they sacrificed a strange fire before God which he had not commanded them. And a fire came forth from before God consuming them; and they died before the Lord." (Lev 9:23,24;10:1-2)
This must have been some fire! And it sounds like they paid some price for it! The Torah describes a scene like some partying was going on...in other words, Nadav and Avihu were probably drunk, and incapable of performing their sacred service to God. They were warned never to drink before entering the Tent of Meeting in such a condition. But, they did it anyway. And God knew. Of course God knew. They entered the Tent of Meeting and offered a "strange fire", one that God never commanded. That was pretty unexpected and shocking, and it drew more attention to them. So, God, reacted....or overreacted....and poofed them away!
OK, Nadav and Avihu were impulsive and spontaneous, and they weren't behaving like Priests. Did they deserve to die? Moses had acted pretty irrationally when he smashed the Tablets....and he wasn't incinerated. Nadav and Avihu were Priests, Leaders, and they had to be held to a different standard.
They had to wear the proper clothes, handle the sacrifices in a certain way, and use the "commanded fire" properly. But, God needed to teach the Leaders of the community, that when you play with fire, you get burned.