Why did the Torah place the laws of tum'a and tahara in between the stories of the deaths of the sons of Aharon and the laws of entering the Mishkan? Why do the laws of the metzora directly follow the story of the deaths of Nadav and Avihu? It is possible that the answer to this question lies in the mutual exclusivity of the concepts of holiness and tum'a, and the link between tum'a and death. 

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion