1)
What is the meaning of "Vehizartem ... "?
1.
Rashi: It means to separate (the men from their wives [for the Onah, i.e. the night or daytime when she normally becomes Nidah - Moshav Zekenim, from Nidah 63b]. 1
1
From the expression "Nazoru Achor" (Yeshayah, 1:4) and "Nezir Echav" (Bereishis 49:26). See Sifsei Chachamim.
2)
Why does the Torah use the expression 'Misah' and not Kareis (See Bamidbar 19:13)?