TEVILAH ON YOM KIPUR (and Rav's position in the Machlokes)
(Tana Kama): All Chayvei Tevilah should immerse on Yom Kipur, in order to be able to recite Tefilah (Tevilas Ezra).
Similarly, a Nidah and a Yoledes immerse on Yom Kipur night.
A Ba'al Keri who became Tamei after Minchah, may not immerse because, according to the Tana Kama, one recites Ne'ilah after nightfall, in which case, someone who becomes Tamei after Minchah, may immerse later, and not on Yom Kipur (and then recites Ne'ilah, exempting himself from Ma'ariv, like Rav).
(R. Yosi): One may even immerse after Minchah, in order to recite Ne'ilah since, in his opinion, the time for Ne'ilah is before night (not like Rav).
Question: But in a second Beraisa, the Rabanan and R. Yosi seem to have switched positions!?
Answer: The second Beraisa (wherein R. Yosi forbids a Ba'al Keri to immerse after Minchah) speaks when the Tamei man has already recited Ne'ilah.
Question: If he has already recited Ne'ilah, then why do the Rabanan permit his Tevilah?
Answer: They hold that it is always a Mitzvah to immerse as soon as it falls due (and for a Ba'al Keri it falls due by day).
Question: Are we to then infer that R. Yosi does not hold of such a Mitzvah!?
The Beraisa discusses the case of a person with the Name of Hash-m written on his skin.
R. Yosi permits his immersion (even without a bull-rush tied around it) - because of 'Tevilah bi'Zemanah Mitzvah'.
Answer: The first R. Yosi is R. Yosi b'R. Yehudah and the second one is the more commonly known R. Yosi b. Chalafta.
This is supported by the Beraisa in which R. Yosi b'R. Yehudah expressly is lenient regarding Tevilah bi'Zeman.
ONE WHO SEES KERI ON YOM KIPUR
The Tana of a Beraisa permits someone who sees Keri on Yom Kipur to immerse immediately (without washing off the dirt), adding that he will wash it at night.
Question: Of what value is washing at night, after Tevilah!?
Answer: We amend this to teach that everyone should bathe on Erev Yom Kipur, to remove any potential Chatzitzah, in case he sees Keri on Yom Kipur and needs to immerse.
It was taught before R. Nachman that seeing Keri on Yom Kipur is a sign that all his sins are forgiven.
Question: But a Beraisa teaches that his Aveiros are Sedurin (apparently meaning lined up for judgement)!?
Answer: Sedurin means arranged for forgiveness.
(Tana of Bei R. Yishmael): He should worry the entire year (lest his Inuy is being thrown back at him).
If he lives out the year, however, he is assured of going to Olam ha'Ba (his great merit is protecting him).
(R. Nachman b. Yitzhok): This is evident from the fact that in spite of that, when everybody else was 'hungry', he was forced to be 'satisfied', he thus survived the year without affliction, which could only be said of a complete Tzadik.
(R. Dimi): One who sees Keri on Yom Kipur will live long and have many children and grandchildren.