Seeing as the Torah has already informed us that Neveilah is Mutar be'Hana'ah, why does it need to write "Ye'aseh le'Chol Melachah"?
Rashi and Ramban: To teach us that Chelev is not subject to Tum'as Neveilah.
Why does the Pasuk find it necessary to forbid eating Chelev Neveilah and Chelev T'reifah?
Rashi: To teach us that, in spite of the principle 'Ein Isur Chal Al Isur'', the Isur of both Neveilah and T'reifah take effect on that of Chelev, and are subject to Malkos.
Ramban (on Pasuk 25): Because we would otherwise have thought that Neveilah and T'reifah belong to the species from which one does not bring Korbanos 1