TT #19 · Parashas Noach · Second Aliyah · Passuk 7:8
Of the pure animals, and of the animals that are not pure, and of the birds, and of everything that creeps on the ground…
Torah Temimah points to Zevachim 116a (R’ Abbahu — how pure/impure were known before Sinai).
E-Daf image — Zevachim 116a (size=3)
Shas / HebrewBooks PDF of the daf
English: “The pure animals” — Were there pure and impure animals at that time? R’ Abbahu said: Scripture says “and those that came” — from those that came of their own accord (seven pairs = pure; two pairs = impure).
Custom (how the pure/impure categories were identified before Sinai).
The animals that came in sevens were the pure species; those that came in pairs were the impure. Noach did not need prior knowledge of the categories.