M. Weisman, “The Midrash Says,” Chapter “Shemini”: On the eighth day of Holiness, fire came down from the sky and swallowed the sacrifices. After that event, Nadav and Avihu decided that, in spite of that, they must bring their own fire to the altar.
Seven days have gone by (seven levels): Hesed, Gevura, Tifferet, Netzach, Hod, Yesod, and Malchut. The eighth day belongs to GAR, to the upper part, to the part of the head of the level they are on.
The sons feel nothing toward this level, and thus they cannot bring their own fire to it. They could have connected to it through Moses and Aaron, and then they would have received the feeling that it is forbidden to do so.
Their mistake was that they tried to move to an upper level independently instead of connecting to Moses and Aaron.
This means that NHY (the lowest third stage of the level) immediately wanted to connect with HBD when it rose, by skipping HGT, which is the eighth day when the seven levels of HGT NHY, the seven attributes, ascend to the head (Rosh).
Moses and Aaron symbolize the head of the Partzuf (spiritual body) that is comprised of three levels: Keter, Hochma, and Bina.
The bottom part of the Partzuf includes seven levels (Hesed, Gevura, Tifferet, Netzah, Hod, Yesod, Malchut) of which the three lowest levels are Nadav and Avihu.
They wanted to make a correction called a sacrifice that could have brought them to a level above Moses and Aaron, but they couldn’t manage it, and so they died.
All the figures in the Torah are our inner attributes that exist in each of us.
From KabTV’s “Secrets of the Eternal Book” 1/15/14