1)
Why does the Torah insert the word "Sei" both by "Kevasim" and by "Izim"?
1.
Rashi (in Bo, Sh'mos, 12:5): We learn from the fact that the Torah writes "ve'Sei Izim" that the term "Seh" also applies to goats.
2.
Targum Yonasan: To preclude the children of Tamei species, and children of a crossbreed of a Tahor species with a Tamei one.
2)
Why does the Torah write "Sei Kesavim" (plural)?
1.
B?choros, 7a: To teach us that it is only Kasher if its father and mother are both of a Tahor species ? either a lamb or a goat. Refer to 14:4:1:1.
