Explanation #1: The Rashbam, in Perk Chezkas ha'Batim (Bava Basra, Daf 53a, DH 've'Hashta ka'Aili'), in the Sugya concerning 'Na'al ve'Gadar kol she'Hu be'Nechsei ha'Ger') explains 'Na'al' to mean that he fixed a bolt on the door with which to bolt it, which is in fact, an act of building ...

Explanation #1 (cont.): But locking the door of the property of the Ger is not a Chazakah ...

Reason: Since it is akin to 'Mavri'ach Ari (chasing a lion off one's friend's property)'.

Implied Question: Even though with regard to renting houses, the Gemara at the beginning of Pesachim (Daf 4a Tosfos DH 'Im') says that once the owner hands over the keys, the onus lies on the renter to search for Chametz, and it is also effective with regard to acquiring a house ...

Answer: That is specifically in connection with selling or renting out a house to one's friend, but as far as the property of a Ger is concerned, who hands him the keys, that he should acquire (the house)?

Question: The Ri queries the Rashbam however, in that the Gemara here clearly implies that handing over the key does not acquire, and that it is no more than if one were to say 'Go make a Chazakah and acquire!'?

Question (cont.): And it is regarding Chametz exclusively that handing over the key is effective, because the onus of searching for Chametz lies on whoever has the key, seeing as he is able to enter the house

Explanation #2: And what he says that one does not acquire with locking the door, is not correct either ...

Source: Seeing as, in Gitin (Perek ha'Zorek, Daf 77b), the Gemara says, in connection with a Get 'Let her go and lock the door and open it!'.

Implied Question: Even though it is forbidden to acquire on Shabbos?

Answer: In the case of a 'Sh'chiv Mera' (a man on his death-bed) it is permitted - so that he does not lose his sanity (and die).

Proof: In fact, in 'Chezkas ha'Batim' (itself, on Daf 57a) this is also clearly stated, in connection with 'These are the things to which Chazakah applies, and these are the things to which it doesn't ... '. And on the question 'What is the difference between the Reisha and the Seifa?'

Proof (cont.): Rava answers 'Whatever acquires by the property of a Ger, also acquires by the property of one's friend, and whatever does not acquire by the property of a Ger, does not acquire by the property of one's friend, either'.

Proof (cont.): That being the case, when the Tana says in the Seifa that 'If he brings the chickens into the house, it is a Chazakah, by Nechsei ha'Ger, he acquires it too.

Proof (concl): And the reason that he acquires it is because, after placing the chickens there, he probably locked the door, in order to guard them. So we see that locking the door is sufficient (to acquire).

Further Refutation of Explanation #1: Nor can one compare locking the door to chasing away a lion ...

Further Refutation of Explanation #1 (cont.): Because it is specifically where one places a clod of earth, thereby stopping the water from entering the field, does the Gemara say in 'Chezkas ha'Batim' (Bava Basra, Daf 53a) compare to 'Mavri'ach Ari', but 'Na'al', where one locks the door before everyone, letting nobody into the house, is clearly a sign that the house belongs to him, and he therefore acquires it with locking alone.

Implied Question: And when the Gemara states there that 'If Reuven builds a mansion in the property of a Ger, and Shimon comes and puts in the doors, he (Shimon) acquires it' ...

Answer: It mentions the norm., in that it is normally the person who puts in the doors who locks them ...

Answer (cont.): But in fact, he would acquire it even if he merely locked the doors, without building them.

Opinion #1: This means that the fact that the pit was open became known, in which case, he presumably heard about it.

Opinion #2: According to Shmuel, he will not become Chayav with hearing alone, as he does not take hearsay seriously, until he is informed personally.

Opinion #3: Whereas Rebbi Yochanan holds that he is not Chayav until he is informed personally and has had time to hire workers to cut down cedars (with which to cover the pit) ...

Opinion #3 (cont.): And we give the same time-period to the second partner, only he does not to be informed, since he already knows about it.

Opinion #2 (cont.): But Shmuel maintains that as soon as he is informed, he is obligated to place guards next to the pit, to prevent anyone from falling into it.

Explanation: Rashi explains that if camels fell into the pit, it is not necessary to mention that he is Chayav, seeing as regarding camels he is considered negligent.

Proof: And this is also implied by the Lashon of the Gemara.

Reason: And the reason for this may well be because, even though camels are not at all frequent, one needs to take into account the possibility that camels may come and fall into the pit.

Conclusion: One need not however, take into account the possibility that camels might come and break the cover of the pit, and that oxen will then fall into it.

Question: Initially, the Gemara wants to prove from the Reisha that he is Patur. In which case, the Seifa states 'Lo Kisahu ka'Ra'uy', not because it comes to teach us anything, but because ('Aidi') the Reisha says 'Kisahu ka'Ra'uy'.

Question (cont.): In that case, how can it now prove anything from the Seifa?

Answer: To be sure, initially, when it was not able to give any other reason, it had to say 'Aidi ... '. But now that it is able to find a Chidush, it is logical not to say 'Aidi'.

Clarification: This means that, if at first, camels passed and then oxen, which fell into the pit, it is obvious that he is Chayav, seeing as he was negligent ...

Reason: ... seeing as camels are frequent, or even if the only pass from time to time he ought to have taken that into account.

Clarification (concl.): ... and the She'eilah is therefore where camels did not come, and the oxen fell in because the cover turned wormy - what is now the Din? Do we say 'Migu' (since he was Poshe'a regarding camels ... ) or not. And the Gemara concludes that we don't say 'Migu'.

Question: Even if we don't say 'Migu', why is he not Chayav based on the principle 'Techilaso bi'Peshi'ah' (regarding the oxen, bearing in mind that camels might come before the oxen) 've'Sofo be'Oneis' (since it turned wormy)'?

Answer: The Riva answers that we only say 'Techilaso bi/'Peshi'ah ve'Sofo be'Oneis, Chayav' there where the Oneis is the result of the Peshi'ah, whereas here, it is is not ...

Reason: ... seeing as, even assuming the pit had been covered properly with regard to the oxen and the camels, the cover would have turned wormy.

Proof: And this is also implied in 'ha'Mafkid' (Bava Metzi'a, Daf 36b & 37a) where the Gemara says, in the case where he was negligent and the animal went into the meadow, that even according to the opinion that 'Techilaso bi'Peshi'ah ve'Sofo be'Oneis, Chayav', there he is Patur ...

Proof (cont.): ... because, since it is the Angel of Death that killed it, what difference does it make to the Angel of Death whether it is here or there?

Question: In 'ha'Koneis', (later on Daf 56a & 56b) in the case of where the wall broke in the night, the Gemara asks, if it was a weak wall, why he is Patur, if it dug underneath it, since it is a case of "Techilaso bi'Peshi'ah ve'Sofo be'Oneis"? '

Question (cont.): And there the Oneis did not come about as a result of the Peshi'ah, since the animal could have dug underneath the wall even if it was a strong one?

Answer: Rashi explains there that the animal dug underneath the wall and the wall collapsed due to the digging - in which case the Oneis did indeed come about as a result of the Peshi'ah, because had the wall been strong, the digging would not have caused it to collapse.

Question: At the end of 'ha'Po'alim' (Bava Metzi'a, Daf 93b, and 94a) in connection with the shepherd who left his flock and returned to the city, and a lion came and took a sheep', Abaye asks that that too, is a case of 'Techilaso bi'Peshi'ah ve'Sofo be'Oneis'? ...

Proof: ... because, if he went to town at a time when people do not generally go, then even if he would not have been able to save the sheep even if he had been there, he ought to be Chayav?

Question (cont.): ... and there the Oneis is not the result of the Peshi'ah, since what difference does it make whether he is here or there, seeing as he could not have saved the sheep anyway?

Answer #1: The Rivam answers, citing the Rif, that. according to Abaye he is indeed Chayav even there where the Oneis is not the result of the Peshi'ah ...

Source: ... as is implied in 'ha'Mafkid' (Ibid.) where he says that it is obvious that he is Chayav according to the opinion that holds ''Techilaso bi'Peshi'ah ve'Sofo be'Oneis, Chayav" ' ...

Source (cont.): ... implying that, according to the opinion that holds 'Chayav', Abaye is happy with the ruling even without the reason that 'the air of the meadow killed it'.

Answer #2: Moreover, in any event, the Ri explains the Sugya there in a way that the Kashya is non-existent ...

Conclusion: ... and here is not the place to elaborate further (See Hagahos ha'G'ra).

Question: The Ri asks however, how the Gemara can resolve the She'eilah from the case where 'an ox that is a Chashu fell into it, seeing as it is not comparable to it (the She'eilah), because, as far as a regular ox is concerned, it is correct not to consider him a Poshe'a via the 'Migu', since he is not negligent at all vis-a-vis a regular ox ...

Question (cont.): ... whereas in the She'eilah he is Poshe'a regarding the oxen, there where camels weaken the cover, in which case the 'Migu' will be effective to be considered a Poshe'a regarding the oxen if it becomes wormy as well?

Answer: The Ri therefore explains that 'Kisahu she'Lo ka'Ra'uy li'Gemalim' speaks where the moment the camels pass, the cover of the pit will cave in ...

Answer (cont.): ... and in such a case, there is no Peshi'ah regarding the oxen at all, rendering it 'Techilaso ve'Sofo be'Oneis, because if camels do not come, it is fit for oxen, and if they do, it will cave in completely - the regular oxen will see it and will be careful not to fall in.

Answer (cont.): Nevertheless, there is certainly a'Migu', and the Gemara is justified in asking whether we say 'Migu' - since he is Poshe'a for camels, he is also Poshe'a for oxen, if the cover becomes wormy.

Answer (concl.): According to this, 'Techilaso bi'Peshi'ah ve'Sofo be'Oneis' is not applicable here, since it is 'Techilaso ve'Sofo be'Oneis'.

Question: Now that the Gemara knew that a Shor Pike'ach is Patur - seeing as the owner of the pit is not Poshe'a, what is then the She'eilah? Why does he not resolve it from the Mishnah, which states 'Shor Chashu, Chayav', from which we can extrapolate that regarding a Pike'ach, he is Patur, and that we do not say 'Migu'?

Answer #1: The Gemara currently thinks that one is Patur on all oxen by day, both Shotim and Pikchim, and Chayav by night ...

Answer #1: ... and the reason that it mentions Cheresh ('Chashu') is because we would otherwise have thought that one is not Chayav for a Cheresh, as the Gemara wants to say later (on Daf 54b) 'Its deafness caused it to fall in'.

Implied Question: And from the fact that the Tana does not say 'Migu' - since he is Poshe'a by night, he is also Poshe'a by day' ...

Answer: The Gemara cannot resolve the She'eilah, seeing as they are not comparable, since at that moment (when it fell in the day), it is an Oneis.

Answer #2: Furthermore, says the Ri, it is possible to say that he knew very well that on a Pike'ach he is Patur and on a Cheresh he is Chayav ...

Answer #2 (cont.): ... and granted, the Tana does not say there 'Migu', because the Pike'ach is considered as having damaged itself, as if it deliberately cast itself into the pit, and the Torah only declares the owner liable, where the victim is unable to spot the danger facing it ...

Answer #2 (concl.): ... but when it falls as a result of worms, that is where he ought to be held liable via a 'Migu', since the argument that 'It should have looked where it was going' does not apply.

Conclusion: But in the Maskana, when the Gemara resolves the She'eilah, it does not consider this distinction significant.

Question: Why does the Gemara ask the She'eilah where camels are frequent, it could just as well have asked it even if they were not frequent at all, since, as far as the camels are concerned, he is considered a Poshe'a, and he would be Chayav if they were to fall into the pit, even if they were not frequent ...

Source: ... as is evident in the earlier She'eilah?

Answer: If the camels were not frequent or even if they came occasionally, it is obvious that we would not say 'Migu', since the Chiyuv regarding camels does not occur frequently.