Explanation #1: Rashi explains that it is in order to avoid transgressing 'Bal Yera'eh u'Bal Yimatzei'.

Question: The Ri queries that however, on the grounds that the Chametz requires 'Bitul', as the Gemara states later (on Daf 6:) 'Someone who searches for Chametz, still needs to declare it nullified. And since, min ha'Torah, Bitul alone will suffice, why did the Chachamim necessitate Bedikah at all?

Explanation #2: The Ri therefore explains that, even though Bitul alone will suffice, the Chachamim were strict and required that one search and destroy the Chametz as well, so that one does not come to eat it.

Proof: As is implied later (on Daf 10:), where Rava discussing about a loaf of bread in the rafters ... asks 'or perhaps it might fall and one will come to eat it.

Implied Question: Why were the Chachamim more stringent here than by other Isurei Hana'ah, which they did not require to be burned?

Answer #1: Because Chametz is permitted the whole year round, and is only forbidden on Pesach, so that one is not used to separating from it - as the Gemara says later on (Daf 11.)

Answer #1 (cont.): And it is not therefore comparable to Basar be'Chalav, Orlah and Kil'ayim, whose prohibition is permanent.

Implied Question: And the reason that they did not obligate a Nazir to destroy his wine (which, like Chametz, is only temporarily forbidden)?

Answer: Is because others are permitted to drink it.

Answer #2 (based on manuscript of Tosfos): [Moreover, it is not comparable to Orlah and other Isurin, since a. Chametz is subject to Kareis and b. people do not keep away from it all the year round.]

Answer #3: Alternatively, Chametz is different, since the Torah is particularly stringent with regard to it, inasmuch as it adds the Isur of 'Bal Yera'eh and Bal Yimatzei'. Consequently, the Chachamim were strict and required that one search for Chametz and burns it, even where one has already declared it nullified.

Chidush: It appears to the Rashba that even according to second reason, the Chachamim were stringent with regard to all Chametz, even Chametz Nokshah and Ta'aroves Chametz, even though 'Bal Yera'eh' and 'Bal Yimatzei' do not apply to them ...

Proof: According to Rabeinu Tam at the beginning of 'Eilu Ovrin' (Daf 32.), who explains that 'Si'ur Yisaref' refers to Chametz Nokshah, as is evident there; And there is also an opinion there that holds all the more so a mixture containing proper Chametz, implying that one is forbidden to retain them ...

Proof (cont.): Because otherwise (if it was permitted to retain them), why should they be burned? Let him retain them until after Pesach, and he will be allowed to eat them, even according to Rebbi Yehudah, who only forbids Chametz after Pesach if it is proper Chametz. This is because there are three Pesukim: one for during the period of Isur, one for before the period of Isur and one for after it, as will be explained later (28:).

Proof (cont.): Whereas Chametz Nokshah, for which there is only one Pasuk, even Rebbi Yehudah will concede that it is permitted after Pesach.

Clarification: The Gemara only says 'Ka Salka Da'tach' because the opinion that holds 'Naghi' does not remain with that ...

Clarification (cont.): And so incidentally, it also mentions 'Leilei Mamash'.

Conclusion: Consequently, it is not necessary to emend the wording (and to omit 'u'Man d'Amar Leilei ... ').

Clarification: This does not refer to the Gemara's answer 'ke'Ma'n d'Amar Tzafra N'har'.

Clarification (Part 2): It is as independent statement, and is coming to explain what the Pasuk is coming to teach according to both of the above opinions.

Clarification: The Gemara in Perek ha'Koneis (Daf 60: & 61.), says the Ri, implies that the reasons for this is because of Mazikin (demons), since it learns it from the Pasuk "Li Seitz'u Ish mi'Pesach Beiso ad Boker", and the Pasuk there is a warning against Mazikin ...

Proof: Which in turn, we know, because it extrapolates from it the principle that 'Once the destructive angel receives permission to destroy, he does not draw a distinction between Tzadik and Rasha'.

Ruling: According to that, one should take care to leave in good time' even from one's home town!

Implied Question: In that case, why does the Gemara first mention 'coming in'?

Answer: Because it is the way of the Gemara to do that.

Precedent #1: Like we find (with regard to clambering into and out of a well) that the Gemara in Perek Osin Pasin (Eruvin 21.) states 'clambers up and clambers down' (even though it is obvious that one has to clamber in first).

Precedent #2: And likewise in Perek Bameh Madlikin (Shabbos 34:), where it states that 'Beis ha'Shemashos (the period of dusk) is like the wink of an eye; this one comes in, and that one goes out' (despite the obvious fact that the first leaves before the second one enters).

Question: Rav Yehudah himself (in the Gemara in 'ha'Koneis' that we cited earlier), Darshens this very same D'rashah from the (different) Pasuk of "Lo Seitz'u"?

Answer: The Rashba (or the Ri) explains that we actually need two Pesukim; "ha'Boker Or (in connection with Yosef's brothers)" is needed to teach us that the Din applies in another city, even where there is no problem of Mazikin, such as with Yosef's brothers, who numbered eleven (and Mazikin only start up with individuals). And the reason for the Din there is because of pits into which one is likely to fall.

Answer (cont.): Whereas "Lo Seitz'u" is needed to teach us that it applies even in one's own town, on account of Mazikin.

Clarification: Rabeinu Tam explains that this means up until midday, as is evident in Perek Tamid Nishchat (Daf 58.)

Clarification (cont.): And that is how the sun will shine for the Tzadikim in time to come, when it first appears (at Haneitz ha'Chamah) early in the morning.

Source: The Ri explains that the Gemara takes for granted that day-time lasts until Tzeis-ha'Kochavim ...

Source (cont.): Due to the Gemara at the end of the second Perek of Megilah (Daf 20:), which concludes from a combination of the two Pesukim "And we were doing work from dawn-break until Tzeis-ha'Kochavim" and " ... the night was for us to guard, and the day, to work", that the day begins with dawn-break.

Source (cont.): Likewise, it is evident from there that daytime lasts until Tzeis-ha'Kochavim.

Refutation of Question: Nor can one ask from that Pasuk on the Tana'im in Perek Bameh Madlikin (Shabbos 34:), where Rebbi Yehudah says that Bein-ha'Shemashos lasts from sunset as long as the eastern horizon is red ...

Refutation of Question (cont.): Which, according to one opinion, is up to two thirds of a Mil (seemingly a long time before Tzeis-ha'Kochavim)?

Reason: Because we are simply not experts as to what is called 'Tzeis-Kochavim', as the Gemara says there 'Not (very) large stars that can be seen by day, nor (very) small stars, that can only be seen by night; but medium size stars.

Clarification: However, whenever the colloquial does not conform with the Lashon of the Torah, we go after the colloquial ...

Source: Like we say in Erchin (Daf 19:) regarding someone who undertakes to give the weight of his 'Yad' to Hekdesh, that, although min ha'Torah 'Yad' incorporates the area of the muscles, in the realm of Nedarim, it only goes up to the elbow.

Clarification: The Ri and the Riva explain that this Pasuk is speaking about a father who breaks in to his son's apartment, since a father S'tam has mercy on his son and will not kill him even if the latter stands up to him to save his money.

Clarification (cont.): Hence, the son is not allowed to kill his father unless he knows for sure that he comes with the intention of killing him, in the event that he (the son) catches him breaking in.

Proof: As is evident in Perek ben Sorer u'Moreh (Sanhedrin 72: & 73.) where the Gemara establishes the Beraisa which, commenting on the Pasuk "Im Zarchah alav ha'Shemesh" (in answer to the question 'Did the sun shine on him alone?) explains that if you are absolutely certain that he he does not come in peace, then kill him; Otherwise, don't kill him - by a father breaking in on his son.

Proof (cont.): Whereas the Beraisa which says that 'If you are certain that the person breaking in comes in peace, then don't kill him', is speaking about a son who breaks in on his father.

Explanation #1: Rashi explains that Melachah is forbidden in a place where that is the Minhag.

Refutation: The Ri however, disagrees ...

Question #1: Since in Perek Makom she'Nahagu (Daf 55.) it is clearly evident that according to Rebbi Yehudah, it is an Isur, not a Minhag.

Question #2: Moreover, If the Tana says 'Asur', how can you say 'Minhag?'

Question #3: Furthermore, let us go and see what the Minhag is?

Explanation #2: It would therefore seem that their Machlokes is in a case where it is Vaday Asur - and in Galil, just as Beis Shamai and Beis Hillel argue there in the Mishnah.

Clarification: According to the Conclusion, that 'Or' means literally light, Rebbi Eliezer ben Ya'akov mentions the Shi'ur for his ruling at the beginning of the day; whereas Rebbi Yehudah mentions 'Hanetz ha'Chamah', which is when the workers begin to work, which is after the sun begins to shine.

Source: Like the Gemara says in 'ha'Socher es ha'Po'alim (Bava Kama 83: & 84.) 'A worker must arrive in his own time, but leaves in the time of his employer (i.e. on his way home) as the Pasuk writes in Tehilim "The sun shines and they [the animals are gathered in] a man goes out to work".

Conclusion: Rebbi Eliezer ben Ya'akov holds neither like Beis Shamai (who forbids the night, too) nor like Beis Hillel (who permits until Hanetz ha'Chamah).

Alternative: According to the initial understanding, that 'Or' means like Beis Shamai, Rebbi Eliezer ben Ya'akov will hold that Beis Shamai and Beis Hillel do not argue over this point.

Clarification: Where there is no logical reason to differentiate between them ...

Clarification (cont.): But there where there is - such as regarding the ruling prohibiting eating from Minchah-time and onwards on account of having an appetite (for Shabbos) and similar cases, the Gemara is not speaking.