The Ramban suggests that Har Ha’Har, upon which Aharon died, was actually a mountain ridge stretching from Mosera to Kadesh. Aharon climbed up to the ridge in Kadesh and died on top opposite Mt. Mosera. This explanation resolves the apparent contradiction concerning the place of Aharon’s demise, Mosera or Har Ha’Har.
Horav Yekusiel Grunwald, z.l., offers a homiletic rendering of this pasuk which suggests a profound message. Mosera was the place where brother fought against brother with casualties falling on each side. After Aharon’s death, the Clouds of Glory departed, causing much consternation among Bnei Yisrael. Afraid of war with the king of Arad, the people appointed a chief to take them back to Egypt. In Mosera, the tribe of Levi battled against them. In the ensuing battle, both sides suffered. The first blood to be shed between brothers was in Mosera. In reality, the spirit of Aharon, which is synonymous with peace, departed in Mosera. Even when a person physically dies, his spirit and legacy can live on in the heart and mind of his followers. His demise is final only when this spirit no longer serves as an inspiration to others.