What are the implications of the words "Lo Yavo"?
Rashi: To forbid a Kohen even to enter the Ohel in which a Meis is lying.
And why does the Torah insert the word "Nafshos"?
Having just forbidden the Kohen Gadol to render himself Tamei Meis, why does the Torah find it necessary to add "le'Aviv u'le'Imo Lo Yitama"?
Rashi: To extrapolate that he may (and should) render himself Tamei for a Meis Mitzvah.