Rashi on Deuteronomy 15:21/רש"י על דברים ט״ו:כ״א

1מום [AND IF THERE BE] ANY BLEMISH [THEREIN, IF IT BE LAME, OR BLIND, OR HAVE ANY ILL BLEMISH, THOU SHALT NOT SACRIFICE IT …] — any blemish is a general statement,

2פסח או עור LAME OR BLIND is a particularization,

3כל מום רע ANY ILL BLEMISH — it again comprises them in a general statement. How is it with the blemishes particularised? They have the characteristic that each is a visible (external) blemish and the animal never returns naturally to its original condition (i.e. never becomes free from the blemish). So, too, the general statement includes all such blemishes that are visible and incurable [while in the case of a transitory blemish the animal may be sacrificed when the blemish has disappeared] (Bekhorot 37a; cf. Sifrei Devarim 126:2).