With what does the Tamei Meis become purified?
Rashi: With ?the ashes? 1 (?Eifer? - masculine) - of the cow - not the cow (since Parah is feminine).
With water sanctified with the ashes. Rashi said the ashes to explain "Hu Yischatei Bo" (which is masculine singular. Water is plural, and Parah is feminine. - PF)
R. Bachye: Hence the Minhag to wash one?s hands after burying a Meis - to hint at the Mei Eifer Parah.
Which also hints at Techi?as ha?Meisim, when the whole world will becmw purified from Tum?as Meis - as the Navi writes in Yechezkel 36:25 "Vezaarakti Aleichm Mayim Tehorim u?Tehatem". See R. Bachye.
Having written that a Tamei Meis who is sprinkled on the third and seventh days is Tahor, why does the Torah need to add that if he isn't sprinkled ... he is Tamei? Why is it not self-understood?
Kidushin, 62a (citing R. Meir): Because if both sides of a stipulation - the positive and the negative - are not stated, like the stipulation of the B'nei Gad and the B'nei Reven, it does not take effect.
Oznayim la'Torah: Because, bearing in mind that ll other Tun'os become Tahor via Tevilah alone, we maight otherwise have thought that sprinkling with the Eifer ha'Parah is a Mitzvah, but is not crucial to the Taharah.
What happens to a Tamei Meis who is not sprinkled with the ashes on the third day of his Tum'ah?
Rashi (in Kidushin 62a), B'chor Shor and Chizkuni: On whichever day he is sprinkled the first time, he must receive the second sprinkling four days later. 1
Rambam (Hilchos Parah Adumah 11:2): He may receive the latter sprinkling on day seven, or any day afterwards.
Aderes Eliyahu (also in Chumash ha'Gra): It does not help to receive Haza'ah: afterwards - on days four and eight. Even though Pasuk 12 implies like this "ve'Im Lo? Lo Yit'har", this is astounding! The Chachamim decreed not to sprinkle on Shabbos (Eruvin 67b). If so, one who became Tamei on Sunday or Thursday can never become Tahor! Perhaps if he is exposed to Tum'as Meis again, he can receive Haza'ah on days three and seven from the latter Tum'ah. However, a Kohen or Nazir may not do so! This requires investigation. (PF)
In Kidushin, 62a, the Gemara say that R. Chanina ben Gamliel, who extrapolates the positive from the negative, needs "ve'Im Lo Yischata", in case we say that it is a mere Mitzvah Lechatchilah to sprinkle on both days three and seven, but Bedi'eved one of them suffices. We already know this from "Chukah", which teaches that what is written is Me'akev?
Perhaps he holds like R. Yonason, who normally interprets 'Vav' to mean 'or'. Here, he agrees that one must sprinkle on both days, due to the repetition. 1 (PF)
However, the Gemara should have explained that he holds like R. Yonason. Perhaps this is why Moshav Zekenim left this question difficult! (PF).
