Seeing as the Neveilah of a Tahor animal is not Metamei one who eats it (as will be clarified in 22:8), what is the Torah saying here?
Rashi (citing Nidah, 42b): The Torah is teaching us here that the Shi'ur of touching and carrying a Neveilah is a k'Zayis 1 (which is the Shi'ur Achilah).
Rashbam: It is teaching us that sometimes, eating Neveilah 2 without touching it renders a person Tamei.
Moshav Zekenim citing Chulin 71a: The Torah teaches that one who eats Nevelah and immerses 3 is Tahor at night, even if he ate just before nightfall, and the Nevelah is intact in his stomach. This shows that Tum'ah Belu'ah (swallowed or enveloped) is not Metamei.
Rashi writes that the Neveilah of a Tahor animal is not Metamei one who eats it. How is it possible to eat Neveilah without [becoming Tamei through] touching or carrying it?
Rashi: It is possible there where Reuven's friend sticks the food into his (Reuven's) throat. 1
He himself put half a k'Zayis in his mouth (refer to 11:40:2:1*), and then another half-k'Zayis, and swallowed them together. (PF)
Mizrachi: Tum'ah is not Metamei through touching in covered places. According to Abaye there, even if he sticks it in his throat, it is considered Belu'ah, and it is not Metamei through moving (swallowing) it. According to Rava, it is not Belu'ah; a Gezeiras ha'Kasuv is Metaher one who eats Nivlas Behemah. (The Gemara there discusses sticking the food in his mouth. All agree that Tum'as Maga applies to the tongue (Kidushin 25a)! We must say that it did not touch his tongue, for a Chatzitzah (e.g a leaf) separated the Tum'ah from his tongue, or it was stuck in his throat, - PF)
Seeing as someone who merely touches a Neveilah becomes Tamei (the previous verse), why does the Torah need to teach about one who carries it?
Having already taught us the Din of touching and carrying a Neveilah (above 24, 25), why does the Torah repeat it here?
Ramban #2 (citing Toras Kohanim): The earlier Parshah is referring to the Tum'ah of Ever min ha'Chai, and the current one, to Tum'as Neveilos. 2
Why does the Torah insert "ha'Ochel mi'Nivlasah, and why did it insert it here, regarding a Tahor animal?
Ramban #1, Moshav Zekenim: To teach us that the Tum'ah is not greater due to the fact that he also ate it - and it mentions it here 1 because one is more likely to 'mistakenly' eat it, bearing in mind that the animal was slaughtered. 2
Rashi writes that our verse teaches about the Shi'ur of Tum'as Maga and Masa. It says here that he is Metamei Begadim. This shows that we do not discuss Maga, like it says (about Mei Chatas) in Yuma 14a!
R. Chaim Paltiel: There, the Torah did not say said Nosei, rather, "u'Mazeh"; it mentioned Maga only after this, so we cannot say that Mazeh means touching. Here, Noge'a was written before eating, so eating teaches the Shi'ur for touching. We would have said that there is no Shi'ur for Masa, if not that the Reisha mentions Tum'as Begadim, which applies only to Masa. Also, if eating did not teach about the Shi'ur for Masa, the Torah would have written about Masa only Tum'as Begadim, but not "v'Tamei Ad ha'Erev", which applies even to Maga. 1 .
It seems that Moshav Zekenim answers that since it is needed to teach about Masa, for which there is no challenge, it is needed also for Maga. I did not understand this. (PF)
If one carries Neveilah, which garments is he Metamei?
R. Chaim Paltiel: It is only the clothes that he was wearing at the time.
Moshav Zekenim: While carrying it, he is an Av ha'Tum'ah [regarding most Kelim]; he is Metamei clothes that he touches, whether or not he is wearing them, but not people or Kli Cheres.