Gemara

(Mishnah): After Melikah, if a Tevul Yom (one who was Tamei and immersed today; he remains slightly Tamei until nightfall) or Mechusar Kipurim (a Tamei person who needs to bring a Korban, and has completed his Taharah process except for the Korban) touches Chatas ha'Of, it becomes Pasul.

Inference: It becomes Pasul (disqualified) it, but it will not become Tamei (able to disqualify other Kodshim).

(Beraisa - Aba Shaul): A Tevul Yom is a Rishon l'Tum'ah regarding Kodshim. (I.e. if he touches Kodesh, it becomes a Sheni, i.e. a second-level Tum'ah);

R. Meir says, a Tevul Yom makes Kodesh become Tamei (a Shelishi, which can disqualify other Kodesh) and makes Terumah become Pasul (a Shelishi. It cannot disqualify other Terumah);

Chachamim say, just like he disqualifies (but is not Metamei) food and drink of Terumah, he disqualifies food and drink of Kodshim.

Chulin 87b (Mishnah): Fluids of a Tvul Yom are like liquids that he touches. They are not Metamei;

The fluids of all other Temei'im, whether they have a light or severe Tum'ah, are like fluids that they touch, i.e. a Rishon l'Tumah, except for fluids that are Avos (sources of) Tum'ah.

Nidah 71b (Mishnah): Beis Hillel say, they retracted to say that she is like one who touched a Tamei Mes regarding Kodshim;

Beis Shamai say, she is like a Tamei Mes.

Our Mishnah is like Aba Sha'ul, who says that a Tevul Yom is like a Rishon regarding Kodesh.

(Mishnah - Beis Shamai): She must immerse again after Yemei Tohar finish;

Beis Hillel say, she need not immerse again.

Yevamos 74b (Abaye): It says about a Yoledes (one who gave birth) "until the days of her Taharah are completed". This implies that once the days are completed, she is Tehorah;

Contradiction: It also says "the Kohen will atone for her and she will be Tehorah"!

(Resolution): The first verse teaches when she can eat Terumah. The latter teaches when she may eat Kodshim.

Sotah 29b (Beraisa - R. Yosi): A Kal va'Chomer teaches that Kodshim can become a Revi'i:

A Mechusar Kipurim may eat Terumah, but he disqualifies Kodshim. Food that is a Shlishi is forbidden regarding Terumah, all the more so it disqualifies Kodshim!

A verse teaches that Kodshim can become a Shlishi. The Kal va'Chomer teaches that it can become a Revi'i.

Objection (R. Yochanan):.The Kal va'Chomer can be refuted!

If a Tvul Yom touched a food, even though the food is Tamei regarding Terumah, it does not make a Revi'i in Kodshim! (The Gemara brings the Beraisa in Me'ilah 8a).

Answer (Rav Papa): The question assumes that R. Yosi holds like Chachamim. Perhaps he holds like Aba Sha'ul!

Rejection: If he did, he would learn a Revi'i in Kodshim from a food that a Tvul Yom touched!

A Tvul Yom is Tahor regarding Chulin, yet he disqualifies (mid'Oraisa) two more levels of Kodshim foods. A Sheni is Tamei regarding Chulin, all the more so it disqualifies two more levels of Kodshim!

Chagigah 21a (Mishnah): An Onen or Mechusar Kipurim must immerse for Kodesh, but not for Terumah.

Pesachim 92a (Mishnah): An Onen immerses and eats Pesach at night.

Parah 11:4 (Mishnah - R. Meir): Anyone who must immerse mid'Oraisa, after immersing he is Metamei Kodesh and Posel Terumah;

Chachamim say, he is Posel Kodesh and Terumah, and he is permitted Chulin and Ma'aser.

RISHONIM

Rambam (Hilchos Avos ha'Tum'ah 10:3): If a Tevul Yom or Mechusar Kipurim touched a Kodesh food or drink, it is a Revi'i.

Rambam (Hilchos Mishkav u'Moshav 5:4): If a Yoledes immersed after seven days after giving birth to a boy, or after 14 days after giving birth to a girl, regarding Kodesh she is like a Rishon l'Tum'ah who still did not immerse, or like one who touched a Nidah or a Tamei Mes and he still did not immerse. She is Metamei Kodshim like a Vlad ha'Tum'ah (Rishon l'Tum'ah) until Yemei Tohar finish, and then she is totally Tahor.

Rashi (Chagigah 24a DH Eino): R. Yosi learns a Shelishi in Kodshim from a verse, and a Revi'i from a Kal va'Chomer. Normally, a Kal va'Chomer cannot teach a bigger Chidush than the source. This is called 'Dayo'. Dayo does not apply if then the Kal va'Chomer would not teach anything. According to the opinion (Bava Kama 25a) that says that Dayo even in this case, a Revi'i in Kodshim is a mere stringency mid'Rabanan.

Tosfos ha'Rosh (Sotah 29b DH Laisi): It would be better to learn from a food that a Tevul Yom touched than from a Tevul Yom, for it teaches that a Shelishi makes a Revi'i, and about a food that a Tevul Yom touched. Also, one cannot challenge this due to Dayo.)

Tosfos (Pesachim 14b DH v'Ilu): A Kal va'Chomer should teach that if a Tevul Yom made a Shelishi, it makes a Revi'i in Kodesh. A Mechusar Kipurim makes a Revi'i, even though he is permitted Terumah. All the more so the Shelishi of a Tevul Yom, which is Pasul for Terumah, makes a Revi'i in Kodesh! If a verse teaches that his Shelishi does not make a Revi'i, when the Gemara makes this Kal va'Chomer, it should have said that a Tevul Yom disproves this. The Yerushalmi asks this.

Pnei Yehoshua (14b DH Mihu): I do not understand Tosfos. He asks R. Yochanan's question in Sotah! According to Rashi, we can distinguish between our Sugya and that in Sotah. Also Tosfos in Me'ilah connotes like this. However, why does our Tosfos cite the Yerushalmi, when it is also in the Bavli?

Tosfos (Zevachim 17b DH ka'Savar): Rabah says that a Mechusar Kipurim of Zav is like a Zav. Rashi explains that regarding Kodshim, it is as if he did not immerse. If he touched them, they become a Rishon. This is difficult. The Mishnah says that a Tevul Yom or Mechusar Kipurim is only Posel Kodshim! R. Tam said that 'Posel' is due to Tevul Yom, but a Mechusar Kipurim is Metamei Kodshim. R. Chaim challenged this from Sotah 29a, which says that a Mechusar Kipurim is Posel Kodshim. Also, in Nidah we say that only Aba Sha'ul holds that a Mechusar Kipurim is Metamei Kodesh.

Tosfos (Chulin 87b DH Mashkeh): The Gemara here and in Nidah is according to Aba Sha'ul, who says that a Tevul Yom is a Rishon regarding Kodesh. R. Akiva in Pesachim (19a) is like Chachamim in Me'ilah, who say that he is only Posel Kodesh.

Tosfos Yom Tov (Nidah 10:7): The Rav (Bartenura) says that she need not immerse after Yemei Tohar for Terumah, but she must immerse for Kodesh, like Chagigah 21a. However, there the Rav says that a Mechusar Kipurim is Posel Kodesh even after Kaparah. Here we require Tevilah only for eating! The Yerushalmi's text of the Mishnah in Zevachim forbids a Mechusar Kipurim to touch Kodesh. The Rambam rules like this in Hilchos Avos ha'Tum'ah (12:15), but in Hilchos Mishkav u'Moshav he requires Tevilah after Taharah, i.e. Kaparah. He said unlike this in Hilchos Avos ha'Tum'ah! Rather, in Hilchos Mishkav u'Moshav he requires Tevilah before Kaparah. It is not needed after Kaparah, since the Tevilah before Kaparah is a mere stringency

Chasdei David (Nega'im 8:9 DH MEvi): The Tosefta says 'he brings his Asham and Log of oil in his hand.' It connotes that it discusses the Metzora. However, if so we would not let him carry it in his hand, lest he touch it and disqualify it. The Rambam (Hilchos Avos ha'Tum'ah) says that a Mechusar Kipurim disqualifies Kodesh just like a Tevul Yom. Rather, the Kohen brings them.

Keren Orah (Yevamos 74a DH Hai): Tosfos (72b DH u'Mutar) said that the Gemara did not ask from a Mechusar Kipurim, because a Mechusar Kipurim may not touch Kodesh. The Tosfos Yom Tov says that the Rambam permits touching even before bringing Kaparah. This is difficult, for the Rambam explicitly forbids mid'Oraisa in Hilchos Avos ha'Tum'ah! What was the Tosfos Yom Tov's question? The Rambam explicitly says that a woman during Yemei Tohar is more stringent (and requires another Tevilah afterwards), for even after her first Tevilah she was Metamei Kodshim, whereas any other Tevul Yom is merely Posel. Why did Tosfos (Chulin 87b) answer in his own name that the Gemara in Nidah is like Aba Sha'ul? The Gemara itself explicitly says so! We must say that this was not in his text. It seems that it was not in the Rambam's text, therefore he distinguishes between a woman in Yemei Tohar and other cases of Tevul Yom.

Si'ach Yitzchak (Chagigah 24b DH v'Hinei): The Rambam equates a Mechusar Kipurim to an Onen. After he brings his Kaparah, he must immerse before eating. The Torah forbids only before bringing his Kaparah. After Kaparah, there is no Tum'ah. It is only a stringency to immerse before eating, like for an Onen. However, we can distinguish them regarding touching. An Onen does not disqualify Kodshim even during his Aninus, but a Mechusar Kipurim disqualifies Kodshim before Kaparah. The Sifra says that "veha'Vasar Asher Yiga b'Chol Tamei" includes what a Mechusar Kipurim touches, i.e. before Kaparah.