Pure Intentions, Reward Above

Rav Yitzchok Isaac of Kamarna writes in Heichal Berecha that the souls of Nadav and Avihu left their bodies in a state of union with Hashem and rose above to cling to the Eitz HaChaim, the Tree of Life. Their actions were mistaken, but their intentions were pure. They were punished in this world for what they did, and they were rewarded in the World to Come for the purity of their hearts.