What is "Ach Ma'ayan u'Bor ... Yih'yeh Tahot" - coming to teach us?
Rashi #1, Ramban and Rashbam: It teaches us that a pool of water that is 'attached' to the ground is not subject to Tum'ah 1 and that someone who Tovels in a Mikveh becomes Tahor. 2
Rashi #2 (in Pesachim, 17b): It teaches us that a Mikvah is not subject to Tum'ah.
Rashbam: As the Torah implies above (in Pasuk 34, that only water in a Kli is Mekabel Tum'ah).
Divrei David: The word "Yih'yeh" is superfluous, to teach that it is Metaher one who Tovels in it. And we learn that it cannot become Tamei since it is written here, where the Torah discusses the Dinim of beoming Tamei.
Why does the Torah add the word "Ach"?
Sifra #1: To teach us that, although a spring renders Tahor even via a Kolshehu 1 and when the water is flowing, a Mikveh requrea forty Se'ah and is only Metaher when it is gathered.
See Torah Temimah, note 145.
Seeing as a Mikveh renders Tahor differently than a Ma'ayan, in what way is the Torah comparing them?
Why does the Torah insert the (otherwise superfluous) word "Mikveh Mayim"
What are the implications of " ? Mikveh Mayim Yih'yeh Tahor"?
Zevachim, 25b: It implies that a Mikveh can only be formed via Tahor things ('Havayasan al-Y'dei Taharah T'hei'). Consequently, if the water flows into barrels for Mei Chatas 1 via cane or nut-leaves (which are not subject to Tum'ah) it is KAsher; via one's hand, foot or vegetables (which are subject to Tum'ah), it is Pasul.
See Torah Temimah, note 151.
What is "ve'Noge'a be'Nivlasam Yitma" - coming to teach us?
Rashi and Targum Yonasan: It teaches us that a person who touches a Neveilah becomes Tamei even if he is submerged in a Mikveh. 1
Ramban #1: It teaches us that if water that is detached touches the Neveilah, it becomes Tamei.
Ramban #2: It is referring to all the water mentioned here and in Pasuk 34, and teaches us that water is subject to Tum'ah when it is detached, but not when it is 'attached' to the ground.
Ramban #3 (citing the Sifra): It teaches us that the Neveilah of Sheratzim only renders Tamei someone who touches it, but not someone who carries it without actually touching it.
Otherwise we would learn from a Kal va'Chomer that he remains Tahor ? See Rashi. Refer also to 11:36:152:2.
From where do we know that immersing in a Mikveh renders Tahor, for Tum'os other than Sheratzim?
Ramban: We learn it via a Binyan Av from Tum'as Sheratzim 1 - Sheratzim is the example that the Torah gives from which all other Tum'as derive.
And the reason that the Torah presents it specifically in connection with Sheratzim is - either because it waited until it had covered all the Tum'os before doing so, or because it is the way of Sheraztim to die in fountains and in pits of water (Ramban).
What kind of Mikveh is Metaher?
Moshav Zekenim, and Ri (in Tosfos Bava Basra 66a-b): Any gathering of water that is sufficient for a person to Tovel in - three by one by one Amos, even if it is all Mayim She'uvim (drawn water - that is in a vessel or poured into it from a vessel). 1
R. Tam and Rashbam (in Tosfos Bava Basra 66a-b): See answer #1 - proided it is not made up completely of Mayim She'uvim - which is Pasul mi'd'Oraisa. 2
QUESTIONS ON RASHI
Rashi writes that "Yih'yeh Tahor" teaches that a Mikveh cannot become Tamei, and it is Metaher one who Tovels in it. How can we learn both of these?
Divrei David: The word "Yih'yeh" is superfluous, to teach that it is Metaher one who Tovels in it. And we learn that it cannot become Tamei since it is written here, where the Torah discusses the Dinim of beoming Tamei..
Rashi writes that one who touches Neveilah becomes Tamei even if he is submerged in a Mikveh. What is the Chidush?
Rashi: It overrides a Kal va'Chomer 1 - that if a Mikveh is Metaher a person from his Tum'ah, it should certainly prevent him from becoming Tamei! 2
Sifri: We would otherwise have thought that just like the ground saves [what is attached to it] from becoming Tamei, so too does the water that is 'attached to the ground'..
Mizrachi: Why did Rashi ignore the Sifri (See answer #2) and invent his own Kal va'Chomer? Mei Chatas (water on which ashes of Parah Adumah are placed refutes it! It is Metaher Temei'im, but does not shield Tehorim from Tum'ah. In fact, it is Metamei Tehorim! Gur Aryeh - this is not a refutation. Mei Chatas is not Metaher by itself, without Tevilah, therefore it cannot save.
We must say that even when he touches, it is considered a minority that is not Me'akev Tevilah. If not, it is as if he is not in a Mikveh! The second he lets go (from touching the Neveilah), the Mikveh is Metaher him! This Halachah is relevant to one who left the Mikveh before letting go. And even if he lets go in the water, through Tevilah he is a Tevul Yom. (PF)
