The Daily Ma’amar by our Rebbe Rav Eliezer Berland shlit”a, courtesy of the “Hashem Hu HaElokim” leaflet:
Nadav and Avihu wanted to nullify the world of Igulim [one arrangement of the Sefirot in which the Sefirot and supernal worlds are arranged as a series of concentric circles], and to only leave the column of straight (yosher) [light], and through it, to draw to the world the light of the Infinite, and in this way to return to the Jewish people their level that they had before the sin of the calf at the giving of the Torah, that then their contamination was eliminated, and everyone merited — men and women — to revival of the dead, and from everyone the contamination of the serpent was nullified, and everyone ascended — men, women, and children — to the level of Adam HaRishon before the sin.
And all of this, Nadav and Avihu wanted to bring the Jewish people to the pure level as it was before the sin. If so, why were Nadav and Avihu punished? Rather, their whole sin was that they did everything without receiving permission from the Tzaddik — Moshe Rabbeinu, and they entered without receiving permission from Moshe Rabbeinu.
And Shaul repeated their error, and repeated their error of making the elevation offering without Moshe, and this is the greatest sin, and therefore they were burned, not upon us.
And also, they did not have nullification to one another, and each one took his pan and spoon alone without counseling with his brother, and so they were burned.
To download the Hebrew version, click here