Tafsiran Ulangan 34:7: Rashi, Chizkuni, Ibn Ezra & Or HaChaim

לא כהתה עינו HIS EYE WAS NOT DIM — even after he had died (Sifrei Devarim 357:34).

לא כהתה עינו, “his eye had not become dim;” he had exuded light until the end of his days, as he had when he had returned to earth from Mount Sinai on the last occasion.

The heh in his moisture replaces a vav ; compare “his tent” [Genesis 9: 21]. The word comes from “fresh” [Genesis 30: 37]. Most elderly men are defeated by the forces of dessication.

ולא נס לחו means, nor did the life-sap that was in him depart (Sifrei Devarim 357:35): decomposition had no power over him (had no effect on his body), and the appearance of his face had not changed.