The Lord Spoke to Moses After the Death of the Two Sons of Aaron

Nadav and Avi-Hue went on to sacred space designated for the high priest in accord with a specific procedure. They also could have brought, you know, coals for burning incense from an incorrect source. But one thing that's more apparent is that they're doing something that the high priest was supposed to do and therefore was not prescribed to them because they're not the high priest. The Lord said to Moses, tell Aaron your brother not to come at any time into the holy place inside the veil before the mercy seat so that he may not die.