We learned in our Mishnah that Reuven must move his laundry-pit three Tefachim from the wall of Shimon's pit (i.e. three Tefachim from the border). Rav Nachman Amar Rabah bar Avuhah qualifies this - by confining it to the pit called 'Mechamtzan' (in which the laundry is first soaked for a day or two), but the pit called 'Nadyan' (in which the washing is actually washed, causing the water to splash long distances, must be placed at least four Amos away from Shimon's pit.

We substantiate Rav Nachman's distinction - by citing a Beraisa which gives the Shi'ur of a laundry-pit as four Amos, which can only be reconciled with our Mishnah by explaining it like Rav Nachman.

According to Rav Chiya b'rei de'Rav Ivya's text in our Mishnah, the matter is clearer still - since his version of our Mishnah reads 'Ela-im-Kein Hirchik mi'Sefas Mechamtzan Sheloshah Tefachim'.

We conclude the first group of prohibitions listed in our Mishnah ('Bor Samuch le'Boro ... ') with 've'Sad be'Sid', and we ask whether it should not perhaps read 'O Sad be'Sid'. And we attempt to resolve the She'eilah, based on the second group of prohibitions ('es ha'Gefes ... '), which concludes 'O Sad be'Sid'. Now if the Reisha also reads 'O Sad be'Sid', then why did the Tana not combine the two sets?

We refute this proof however, on the grounds - that the Tana might state 'O Sad be'Sid', and still list them as two sets - because their reasons differ (since the first set is because of wetness, whilst the second set is due to foul air.

We cite the Beraisa where Rebbi Yehudah requires both neighbors to dig their pits in 'Sela ha'Ba be'Yadayim' three Tefachim from the border and to cement them with lime - implying that a pit dug in ordinary earth does not require both steps (in which case, the text in the Reisha of our Mishnah must read 'O Sad be'Sid').

We refute this proof too, however - by equating the Din by any other ground with that of a 'Sela ha'Ba be'Yadayim', and the Tana only mentions 'Sela ha'Ba be'Yadayim' to teach us that even there, three Tefachim distance plus cementing the pit with lime will suffice.

We learned in a Mishnah in Shabbos 'Ein Tomnin (It is forbidden to wrap a cooked dish) Lo be'Gefes, ve'Lo be'Zevel, ve'Lo be'Melach, ve'Lo be'Sid, ve'Lo be'Chol'. The double discrepancy between that Mishnah and ours is - that the Tana there omits rocks, whereas our Tana omits sand.

Rav Yosef answers that the Mishnah in Shabbos omits rocks - because it is unusual to use rocks for keeping hot pots warm

Abaye cites the Beraisa 'Tomnin be'Gizei Tzemer ... u'vi'Leshonos shel Argaman', posing a Kashya on Rav Yosef's explanation - since it is no more common to use shearings of wool and tongues of purple wool for wrapping a hot pot than it is to use rocks, yet the Tana mentions them.

Abaye therefore answers 'Yagid Alav Re'o' - by which he means that the Tana mentions rocks in one place and sand in the other, and it is understood that each one applies to the other place too.

Rava refute Abaye's answer however - because then the Tana should have listed one of the things in one place and all the rest in the other.

Rava finally answers - that the Tana ...

... in Shabbos omits rocks - because, seeing as they would break the pot (or cause it to rust), one would avoid using them for Hatmanah.

... here omits sand - since, although on the one hand, sand keeps things warm, on the other, it keeps cold things cold (in which case, Reuven's sand will pose no threat to Shimon's wall).

And when Rebbi Oshaya forbids Reuven to place his sand within three Tefachim of Shimon's wall - he is speaking specifically about wet sand.

Our Tana does not find it necessary to insert wet sand however, since he has already included a stream of water. Nevertheless, he finds it necessary to insert a a laundry-pit - because we would not have learned one from the other, as we will now explain.

We would not have known ...

... a laundry-pit from a stream of water - because its use is not constant like the latter.

... a stream of water from a laundry-pit - because it is not static like the latter.

We learned in our Mishnah that Reuven must distance his seeds and his plow at least three Tefachim from Shimon's wall. The Tana needs to insert ...

... seeds - by someone who circumvents the need to plow by hand-seeding and then using a spade to cover the seeds.

... plowing - because he is speaking about when Reuven intends to plant trees, in which case he will not be seeding.

Granted, we have already learned that watering is harmful to a wall, and trees require watering - but our Tana is speaking in Eretz Yisrael, about which the Torah writes "li'Metar ha'Shamayim Tishteh Mayim", and which does not therefore need to be watered manually.

The Mishnah in Kil'ayim forbids seeding the area directly above a replanted branch of an attached vine. The Beraisa comments - that one may seed immediately beside the vine.

The Tana must be speaking about a solitary vine (or even up to four vines) - because five vines constitute a vineyard, in which case it would be forbidden to seed even at the side, because of 'Irbuv' (mixing seeds with vines in a vineyard).

Clearly then, seeds grow upwards and not sideways. To reconcile this with our Mishnah, which requires a distance of three Tefachim between Reuven's seeds and Shimon's wall, Rebbi Chaga quoting Rebbi Yossi explains - that it is (not because they directly harm Shimon's wall, but) because they sap the strength from the earth around them, causing the earth underneath the wall to become soft.

Rabah bar Rav Huna learns from the Pasuk in Melachim "ve'Hichrati le'Achav Mashtin ba'Kir ... " - that one is allowed to urinate next to someone else's wall.

He establishes our Mishnah 've'es Mei Raglayim min ha'Kosel Sheloshah Tefachim' - by 'Shofchin', pouring out a relatively large quantity of urine there, but not by urinating.

Rabah bar Rav Huna is proved wrong however - on the basis of a Beraisa, which specifically forbids urinating within three Tefachim of a wall ...

... of bricks - but not one of stones, which only requires a distance of one Tefach.

Consequently, the Pasuk in Melachim, "Mashtin ba'Kir" refers (not to human-beings, but) to dogs (meaning that not even a dog, who tends to urinate against a wall, will remain).

When Rav Tuvi bar Kisna Amar Shmuel says 'Rakik Eino Mema'et ba'Chalon', he means - that a thin loaf of bread (like a Pitah) which fills a window between a room where a corpse is lying and another room, leaving a gap of less than a Tefach, will not prevent the Tum'ah from passing through to the next room.

The reason that he mentions a thin loaf is (not to preclude a thick loaf, but) - to teach us that even a thin loaf, which becomes more dirty than a thick one, retains its identity and does not become Bateil to the wall.

Although anything that is subject to Tum'ah does not prevent Tum'ah from passing through - Shmuel is talking about a loaf which was kneaded with fruit-juice, and which is therefore not subject to Tum'ah.

We query Shmuel from a Beraisa. The Tana rules that a box full of straw or a barrel full of dried-figs is lying on a window-sill that divides between a room in which there is a corpse and another room will prevent the Tum'ah from passing into the second room - provided the straw or the figs would remain intact if one were to remove their respective containers.

To avoid the question that straw has multiple uses (in which case it ought not to prevent the Tum'ah from passing through), we establish the case where it is unfit ...

... to be fed to his animals - because it has turned moldy.

... for making cement - because it contains thorns.

... for fuel - because it is wet.

And we do not contend with the fact that it is fit to fuel a large fire - because a large fire is uncommon.

To explain why the figs are not Chotzetz since theys that are fit to eat - Shmuel establishes the Beraisa by figs that have become wormy ...

... and we back Shmuel's answer with a Beraisa cited by Rabah bar Avuhah.

The barrel itself (that contains the figs) does not prevent the Tum'ah from passing through, despite the fact that the outside of an earthenware barrel is not subject to Tum'ah and is therefore Chotzetz before Tum'ah - because the Tana speaks where it is the mouth of the barrel that is facing the corpse.

Alternatively - he is speaking about a metal barrel, in which case it makes no difference which end of the barrel is facing the corpse.