Why does the Torah use the double expression "b'Fesa Pis'om"?
Rashi #1, Targum Onkelos and Targum Yonasan: "b'Fesa" refers to Ones and "Pis'om", to Shogeg.
Rashi #2: It means that it happened all of a sudden (be'Ones).
Rashi #3 (in Pesachim, 2b): "b'Fesa" refers to Oneis, and "Pis'om", to Meizid.
What are the implications of the word "Alav"?
Rashi: It implies that the Meis died in the tent where he was.
How do we reconcile the fact that, on the one and, the Torah writes that he shaves "ba'Yom ha'Shevi'i", when he is still Tamei, and on the other hand, it writes "b'Yom Taharaso"?
Rashi: To teach us that he shaves on the seventh day, but after he has been sprinkled with the Mei Chatas, which renders him partially Tahor.