Question: He can Mevatel it during the sixth hour [when Chametz becomes forbidden - he will not forget]!

Answer: Since it is forbidden mid'Rabanan then, it is as if it is forbidden mid'Oraisa, it is not considered his, so he cannot Mevatel it:

(Rav Gidal): If one was Mekadesh with wheat of Kordenisa [on Erev Pesach] after the (Rashi - start of; Tosfos - end of) sixth hour, we are not concerned for the Kidushin. (Kidushin is according to Chachamim - they forbade all benefit from the wheat!)

Question: Even after it is forbidden one can Mevatel!

(Beraisa): If one was sitting in a Beis Medrash and remembered that he has Chametz in his house, it suffices to Mevatel it in his heart; the law is the same for Shabbos or Yom Tov.

Granted, we could say that Shabbos refers to the 14th, before Chametz is forbidden - but Yom Tov is always after it is forbidden!

Answer (Rav Acha bar Yakov): The case is, a Talmid in front of his Rebbi (it would be disrespectful for him to leave) remembered that he has a dough in his house and fears that it will become Chametz - he is Mevatel before it becomes Chametz.

Support: It says that he was sitting in a Beis Medrash [but otherwise he would be obligated to destroy it or bake it before it ferments - if it discussed Chametz after it is forbidden, Bitul fulfils Tashbisu as well as any other method]!

(Rabah bar Rav Huna): If moldy bread was found, if Matzah had already become greater [than the amount of Chametz used in that place], it is permitted.

Question: What is the case?

If he knows that it is Chametz, a majority of Matzah does not permit it!

Answer: He is unsure if it is Chametz or Matzah.

Question: Even without a majority of Matzah, we should assume that it is the last thing used there!

(Mishnah): If coins were found [in Yerushalayim] in front of people that sell animals, we always assume that they are coins of Ma'aser Sheni (most animals bought are for Shelamim, from Ma'aser money);

Coins found in Har ha'Bayis are assumed to be Chulin;

In [other places in] Yerushalayim - during the festivals, they are Ma'aser; any other time, they are Chulin.

(R. Shemayah ben Zeira): This is because the markets of Yerushalayim are swept daily (surely they were dropped the day they are found; Har ha'Bayis is not swept, so we follow the majority usage).

This shows that we assume that previous coins were removed, and what is here is recent - the same should apply regarding Safek Chametz (from the start of Pesach, only Matzah was used, we should assume that it is Matzah)!

Answer #1: Since the bread is moldy, surely it is old.

Objection: If the mold proves that it is old, it should be forbidden even if the majority was Matzah!

Answer #2 (Rabah): Rabah bar Rav Huna means, if the days of Matzah (Pesach) had already become many [so it is reasonable that Matzah from the beginning of Pesach would be moldy by now], it is permitted (R. Chananel - after Pesach) (see note 9 in Appendix).

Objection: If it is reasonable that it became moldy from the beginning of Pesach, this is obvious (surely we assume that it is the most recent bread (Matzah), especially since he did Bedikah to get rid of all Chametz)!

Answer: The case is, it is very moldy - one might have thought that this shows that it is definitely Chametz - Rabah bar Rav Huna teaches that this is not so, since many days of Matzah have passed, it is reasonable that warm (freshly baked) Matzah was placed on top of a Matzah [from the first day or Erev Pesach] and made it become very moldy.

Question: We do not follow the last thing used!

(Beraisa - R. Yosi b'Rebbi Yehudah): If a box was used for Chulin and Ma'aser money:

If it is used mostly for Chulin, we assume that money inside is Chulin; if it is used mostly for Ma'aser, we assume that money inside is Ma'aser.

We do not follow the last thing used!

Answer #1 (Rav Nachman bar Yitzchak): The case is, we do not know which was used last.

Answer #2 (Rav Zevid): The case is, piles of Chulin and Ma'aser were put in it [in the same day].

Answer #3 (Rav Papa): The case is, money was found in a crevice (perhaps it is from a while ago, it was not used before because it was not noticed).

(Rav Yehudah): One who checks must bless.

Question: What Berachah does he make?

Answer #1 (Rav Papi citing Rava): He blesses '[Baruch Atah...Asher Kideshanu b'Mitzvosav v'Tzivanu] Leva'er (to get rid of) Chametz';

Answer #2 (Rav Papa citing Rava): He blesses 'Al Bi'ur Chametz'.

All agree that Leva'er connotes [to get rid of in] the future - they argue about Al Bi'ur:

Rav Papi [does not use this phrase because he] holds that it connotes the past; Rav Papa holds that it connotes the future.

Question (Beraisa): One who circumcises blesses '...v'Tzivanu Al ha'Milah' (this shows that it connotes the future)!

Answer: There, one cannot bless 'Lamul', for this implies that he himself must circumcise - but really, someone else could circumcise!

Question: When a father circumcises his son, he should bless 'Lamul' (it is his Mitzvah)!

Answer: Indeed, Rav Papi would say that when a father circumcises, he blesses 'Lamul'!

Question (Beraisa): [One who slaughters blesses] '...v'Tzivanu Al ha'Shechitah'!

Answer: There, one cannot bless 'Lishchot', for this implies that he himself must slaughter, and this is not true.

Question: One who slaughters his Korban Pesach should bless 'Lishchot' (it is his Mitzvah)!

Answer: Indeed, Rav Papi would say to bless 'Lishchot' in such a case!

Question (Beraisa): One who makes a Lulav [bundle on Erev Yom Tov, i.e. ties the myrtle and willow branches to it] for himself blesses Shehecheyanu; when he takes it (the four species) to fulfil the Mitzvah, he blesses 'v'Tzivanu Al Netilas Lulav'.

Answer: There the past tense is appropriate, for he already fulfilled the Mitzvah the moment he picked them up!

Question: If so, why does it say 'when he takes it to fulfil the Mitzvah' - it should say, after he fulfilled the Mitzvah!

Answer: Indeed, it should say this - rather, it says 'to fulfil' for consistency with the Seifa:

(Seifa): One who makes a Sukah for himself blesses Shehecheyanu; when he enters to dwell in it, he blesses 'v'Tzivanu Leshev ba'Sukah'.

The Halachah is, we bless 'Al Bi'ur Chametz'.

Question: All agree that we bless before the Mitzvah - what is the source of this?

Answer: They learned from Rav Yehudah, who taught that on all Mitzvos we bless Over (before) doing them.

Question: How do we know that 'Over' means before?

Answer #1 (Rav Nachman bar Yitzchak): "Va'Yaratz Achima'atz va'Ya'avor Es ha'Kushi."

Answer #2 (Abaye): "V'Hu Avar Lifneihem."

Answer #3: "Va'Ya'avor Malkam Lifneihem va'Shem b'Rosham."

(Bei Rav): The only exceptions are immersion and Shofar.

Objection: We understand why we bless on immersion afterwards - beforehand, the person is not ready; (Rashi - this refers to a Ba'al Keri (one who had a seminal emission), he may not say words of Kedushah before immersing. Tosfos - it refers to a convert, but a Ba'al Keri may bless beforehand. Alternatively, we decree that everyone bless afterwards on behalf of converts; alternatively, everyone blesses afterwards, lest they bless and then get afraid and not immerse.)

But why don't we bless on Shofar beforehand?

Suggestion: Perhaps we are concerned lest it will not be sounded properly.

Rejection: If so, likewise we should not bless on slaughter or circumcision!

Correction (Rav Chisda): Rather, it was taught that the only exception is immersion.

(Mishnah): We check by light of a Ner.

Question: What is the source of this?

Answer (Rav Chisda): A 'chain' teaches that a Ner is appropriate [for "Lo Yimatzei"] - we learn Metzi'ah-Metzi'ah (finding), Metzi'ah from Chipus (searching), Chipus-Chipus, Chipus from Neros, and Ner from Neros:

It says "Lo Yimatzei," and "Va'Ychapes ba'Gadol ha'Chel...va'Yimatzei," and "Va'Achapes Es Yerushalayim ba'Neros," and "Ner Hash-m Nishmas Adam Chofes Kol Chadrei Vaten."

(Tana d'Vei R. Yishmael - Beraisa): On the night of the 14th we check for Chametz by light of a Ner;

There is a hint, not a proof - It says "Lo Yimatzei," and "Va'Ychapes...va'Yimatze," and "Va'Achapes...ba'Neros," and "Ner Hash-m...Chofes..."

Question: Why is the last verse needed?

Answer: One might have thought that a torch is better for checking, just Hash-m will be lenient to use a Ner, so He will not find small sins - "Ner Hash-m...Chofes Kol Chadrei Vaten" shows that a Ner checks very well.