1)

(a)We learn from the Pasuk "be'Veis Eretz Achuzaschem" - that Nig'ei Batim are confined to houses in Eretz Yisrael.

(b)Even in Eretz Yisrael however - the house of a Nochri is not subject to Tum'as Nega'im (see Tos. Yom-Tov).

(c)The Kohen will declare a contaminated house that a Yisrael purchased from a Nochri Tamei (Musgar) starting from that moment (but not retroactively).

2)

(a)The Tana rules that - a round or triangular house - is not subject to Tum'as Nega'im ...

(b)... because the Torah writes twice "be'Kiros ha'Bayis" (see Tos. Yom-Tov), implying that it has to have four walls (and not three, or two or five [see Tos. Yom-Tov]).

(c)... and the same applied to a Nega that appears on ...

1. ... a boat-house ...

2. ... a cabin that is built on the mast of a ship ('Askarya' [see Tos. Yom-Tov]), or ...

3. ... a house that is built on four (horizontal) beams that protrude from an attic (see Tos. Yom-Tov).

(d)If, in the last case, it is built (not on four vertical beams but) on four (vertical) posts (see Tos. Yom-Tov & Tiferes Yisrael) - then it will be subject to Tum'ah - provided the posts form a square (see Tos. Yom-Tov and Tiferes Yisrael)".

3)

(a)The source for the current rulings - is the Pasuk "be'Veis Eretz Achuzaschem".

(b)An alternative text in the middle case reads instead of 'Askarya', 'Achsadya', meaning - a raft.

4)

(a)The Mishnah declares a room one corner of which is covered with ...

1. ... marble ...

2. ... rock or ...

3. ... brick - Tahor.

(b)The fourth item on the Tana's list is - earth (see also Tos. Yom-Tov DH 've'Echad be'Afar).

(c)The reason for this ruling is - that all four walls must be subject to Tum'as Nega'im (which these items are not [see Tos. Yom-Tov]) for the house to be declared Tamei.

5)

(a)Even if the owner subsequently brought stones, wood and earth and added them to the building after the Nega had already appeared - the house remains Tahor ...

(b)... and the same applies to a garment which one completed to a Shi'ur of three by three finger-breadths only after a Nega appeared on it.

(c)The Mishnah finally rules - that for a room to be subject to Tum'as Nega'im, it needs to comprise stones, wood and earth (see Tos. Yom-Tov DH 've'Afar' & 'ad she'Yehei').

6)

(a)We learn from the repetition of the word "ve'ha'Nega" (in the Pasuk "ve'Ra'ah es ha'Nega ve'Hinei ha'Nega" - that the minimum size of a Nega with regard to Tum'as Batim is two G'risin.

(b)According to R. Yishmael, the minimum number of stones for a room to be subject to Tum'as Nega'im is four - one for each wall.

(c)R. Akiva - requires eight, two for each wall.

(d)The basis of their Machlokes lies in the minimum number of stones on which the Nega must appear for the house to be Tamei. According to ...

1. ... R. Yishmael - it is two G'risin on one stone.

2. ... R. Akiva - it is two G'risin on two stones (see Tos. Yom-Tov).

7)

(a)R. Elazar b'R. Shimon disagrees with both earlier opinions. He learns from the fact that the Torah uses both the word "Kir" and the word "Kiros" - that the Nega must appear on a wall that resembles two walls, with reference to a corner ...

(b)... in which case the Nega must appear on the two corner-stones ...

(c)... one ki'G'ris (the size of a square Kilki-bean) on one stone, the second ki'G'ris on the second stone.

(d)The Halachah - is like R. Akiva.

8)

(a)According to the Tana Kama, the minimum amount of wood that is required for the room to become Tamei is sufficient to place under the 'Sh'kof'- (i.e. the lintel and the window-frame).

(b)The minimum amount of wood that is required for the entire room therefore - is sufficient for four such lintels, one for each wall.

(c)R. Yehudah gives the Shi'ur as sufficient to make a 'Sandal' - (i.e. a similar piece of wood that is placed behind Sh'kof, in order to protect the lintel (see Tiferes Yisrael).

(d)The minimum amount of earth that is required for the room to become Tamei is - sufficient to fill in the cracks (see Tos. Yom-Tov).

9)

(a)Both the walls of a feeding-trough and partition walls in a garden ... (see Tos. Yom-Tov) - are not subject to Tum'as Nega'im ...

(b)... because the Torah writes "be'Kiros ha'Bayis" (and these do not fall under the category of'Bayis').

10)

(a)Yerushalayim and Chutz la'Aretz are not subject to Tum'as Nega'im either ...

(b)... because they do not fall under the category of "be'Veis Eretz Achuzaschem" ...

(c)... Yerushalayim - because it was not divided among the tribes (see Tos. Yom-Tov).

11)

(a)We learn from the Pasuk "u'Ba Asher lo ha'Bayis ... ke'Nega Nir'ah li ba'Bayis" - that when the owner informs the Kohen that his house is stricken, this is what he must say, and not 'Nega Nir'ah li ba'Bayis' ...

(b)... even if he is a Talmid-Chacham and the Kohen, an Am ha'Aretz (see Tos. Yom-Yov).

(c)The Kohen then orders all the vessels to be removed from the house.

12)

(a)R. Shimon objects to R. Yehudah's ruling that even bundles of wood (see Tos. Yom-Tov) and bundles of canes (see Tos. Yom-Tov) must be removed from the house - because there is a good reason for clearing the vessels out of the house (as we shall now see), other than just to keep the owner busy.

(b)It appears that he agrees with R. Meir, who says - that wooden vessels and clothes need not be removed, because even in the event that the Kohen declares the house Tamei, they can easily be Toveled ...

(c)... and the same applies to metal vessels.

13)

(a)According to R. Meir, only earthenware vessels must be taken out of the house.

(b)He specifies Pacho and Tifyo. Pacho' means - 'his small earthenware jars'.

(c)Tafyo with a 'Tav'incorporates various kinds of ovens (from the word 'Ofeh'). If it is spelt with a 'Tes' it means - a small earthenware vessel containing liquid which it emits in drops (from the word 'Tif' [a drop]).

14)

(a)R. Meir finally makes two 'Kal va'Chomers'. He extrapolates from the fact that Hash-m takes pity on ...

1. ... the money of a Rasha - that Hash-m certainly has pity on his children, and from ...

2. ... the property of a Rasha - that He certainly takes pity on the property and children of a Tzadik.

(b)It refers to the owner as a Rasha - because Nega'im come on a person first and formost as the result of Lashon ha'Ra (see Tos. Yom-Tov).

15)

(a)The Torah writes "ve'Yatza ha'Kohen min ha'Bayis el Pesach ha'Bayis". We learn from ...

1. ... "el Pesach ha'Bayis" - that the Kohen is not permitted to go home and then shut the door of the stricken house (e.g. by means of a long string) and declaring it Tamei.

2. ... "ve'Yatza ... min ha'Bayis" - that he must leave the house completely and actually step off the threshold (see Tos. Yom-Tov) before shutting the door and declaring the house Tamei.

(b)If at the end of seven days, the Nega has spread - the Kohen removes the stricken stones and takes them to a Tamei location outside the town (see Tos. Yom-Tov Mishnah 7, DH 'el mi'Chutz la'Ir") and dumpss them there.

(c)Then he takes other stones and earth, and replaces the original ones.

16)

(a)The Mishnah rules that the Kohen may not ...

1. ... replace the stones or earth that he has removed with stones or earth from another part of the stricken wall.

2. ... use lime instead of earth to cement the stones.

3. ... replace one stone with two, or vice-versa (see Tos. Yom-Tov).

(b)In fact, the Kohen must replace two stricken stones with two fresh stones - and if three, four or five stones are stricken, he still replaces them with two (larger) stones (see Tos. Yom-Tov).

(c)We learn from the Torah's use of ...

1. ... the plural in the word "ve'Chiltzu es Avanim" - that the 'Rasha's neighbor is obligated to remove the adjoining stones from his side of the wall too, to scrape away the cement (see Tos. Yom-Tov) and to replace them just as the Rasha is.

2. ... the singular in the words've'Afar Acher Yikach ve'Tach es ha'Bayis" - that he is not obligated to cement the fresh stones after replacing the old ones.

17)

(a)If, after the second week, the Nega spreads again - the Kohen orders the room to be demolished (see Tos. Yom-Tov).

(b)The demolished materials - he takes to the Tamei location outside the town and dumps them there.

(c)The Tana draws a distinction between a Pisyon that is close to the Nega and one that is some distance away - in that the former only needs to spread a Mashehu to be considered Tamei, whereas the latter must spread at least the Shi'ur of a G'ris (see Tos. Yom-Tov).

(d)The Shi'ur for a Nega that disappears from the wall and later reappears is - that of two G'risin (see Tos. Yom-Tov).