Tafsiran Ulangan 31:25: Chizkuni, Ibn Ezra & Rav Hirsch

ויצו משה את הלוים, “Moses ordered the Levites, etc.” these are the Levites who had been mentioned in verse 9 as the “priests, who were the sons of the Levites;” Moses was not addressing the tribe of the Levites here. After all, the Levites at large were prohibited from touching the Holy Ark, much less carrying it.

the Levites Scripture employs brevity, as if it had specified, from among the abovementioned Levites, those who are kohanim — but not all of the Levites, since the latter may not touch the Ark.

V. 25. ויצו משה וגו׳ siehe zu S. 9.