Why does the Torah repeat the word "ha'Nega"?
Sifra: To teach us that the Shi'ur of a Nega on a house is two Gerisim. 1
Twice the size of a Nega on the skin and on a garment. See Oznayim la'Torah, as to why we do not learn from here two separate Nega'im.
Why does the Torah write, both here and in Pasuk 39 "be'Kiros ha'Bayis" (in the plural)?
Nazir, 8b: To teach us that Nega Batim is confined to a house with four walls
What is the definition of "Sheka'aruros"?
Rashi: It is when the green or red marks appear deeper than the wall of the house, 1 as the Pasuk itself goes on to explain.
Rashbam: It is a color - like "Yerakrakos" and "Adamdumos".
The Oznayim la'Torah explains this to mean that the green or red marks appear on the plaster, and can be seen on the stones underneath it.
Why does the Torah write "Sheka'aruros O Yerakrakos" (in the plural)?
Oznayim la'Torah: On account of the Shi'ur of two Gerisim
Refer to 14:37:0.1:1.
What size must the Nega be to be Metamei the house?
Nega'im 12:3 #1 (according to R. Yishmael): It must be the size of two Gerisim (a type of large bean) on one or two rocks.
Nega'im 12:3 #2 (accordin to R. Akiva): It must be the size of two Gerisim (a type of large bean) on two rocks.
Nega'im 12:3 #3 (according to R. Elazar b'R. Shimon): It must be the size of two Gerisim (a type of large bean) on two rocks on two walls that meet in a corner. The length is that of two beans, and the width is a bean. 1
Sanhedrin 71a: He holds that there never was a Bayis ha'Menuga, and there never will be (for it is so unlikely that it will occur like this). It was written for us to expound it and receive reward. Birkas Tziyon (71a) - according to Perush h'Mishnayos (Nega'im 12:5) and the Ramban (Vayikra 13:47), any Nega on a house is supernatural! Even so, Hashem would not send it in a shape that is clearly supernatural. R. Eliezer b'Rebbi Tzadok and R. Shimon Ish Kefar Ako saw a 'closed ruin' and a place marked off (due to Tum'ah) due to rocks of a Bayis ha'Menuga (71a). Refer to Devarim 13:17:152:3 and the note there. Refer to Devarim 21:20:152:1*. Daf Al ha'Daf (71a, citing Derech Sichah)
