TT #644 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:04
You shall not muzzle an ox while it is threshing.
Torah Temimah points to Bava Metzia 90b.
TT lemma: בְּדִישׁוֹ.
English: And even to muzzle it outside [before the work begins] is forbidden, for Scripture says ‘You shall not muzzle an ox while it is threshing’ – the Torah said that at the time of threshing there shall be no muzzling.
Derash on the temporal phrase ‘while it is threshing’ (Bavli).
One may not muzzle the animal even before the threshing begins. The prohibition is that the animal must not be in a muzzled state during the work.