Parashas Bo · Shemos 12:5 · TT note 1
Torah Temimah on Shemos 12:5, note 1 (on שֶׂה תָמִים זָכָר) points to Mechilta.
Sefaria — Exodus 12:5
Sefaria — Torah Temimah on Exodus 12:5
Sefaria — Mechilta
English: “A perfect male seh” — seh includes a kid and a lamb, as it is said, “a seh of the sheep and a seh of the goats.” “Perfect” — to exclude one with a blemish. “Male” — to exclude a tumtum, an androgynos, and a female.
Definition of שֶׂה and successive exclusions from תָמִים and זָכָר.
The Pesach may be a lamb or a kid; it must be unblemished and male.