Negaim, Chapter 11, Mishnah 8. This chapter is devoted to Nigei Begadim, the tzara'as that can appear in clothing. An earlier mishnah in the chapter established a fundamental limitation: only white garments are susceptible to tumas nega'im, while dyed, colored cloth is not. Our mishnah takes that rule and asks what happens in a garment that is part white and part colored, since the colored portions stand outside the parshah of nega'im entirely while the white portions are fully included.
The mishnah speaks of a kaita. The Rav explains that this is a type of clothing worn during the hot season; the Targum of kayitz (summer) is kaita. The Aruch LaNer offers a different derivation: the word is Latin, and it refers to what they called a woman's outer coat.
Stripes of white and stripes of color
Such a garment is described as having paspasim. The term is connected to pas yad, the flat part of one's hand, since each band measures roughly a tefach across: white, then dye, then white again. The Rav pictures cloth mottled with a range of tints, green, black, white and similar shades all appearing in the same piece, a garment of many colors.
Here is the ruling: "Kaita sheyeish bah paspasim tzevu'im ulevanim, posim mizeh lazeh", a summer garment containing bands of dye alongside bands of white, and the nega spreads from one band to another. Since dyed cloth is entirely outside the tumah, the spreading under discussion can only mean from a white band into another white band. What the mishnah teaches us is that the dyed band lying between them does not sever the connection: discoloration surfacing in a second white band is reckoned as authentic pisyon of the original nega. This holds true whether the growth shows up when the first week of hesger is completed or when the second one is, and the colored band in between poses no obstacle.
The question of the single white stripe
The mishnah continues with a dialogue that closely parallels a discussion we find elsewhere in these mishnayos. The talmidim asked Rebbi Eliezer: "Vaharei hu pispas yechidi", and what if the garment has only one white stripe? That is, the entire garment is colored except for a single white band, and that whole band has already been discolored by the nega. There is no additional white anywhere for the nega to spread into. Does such a garment still require hesger, or not, since one of the two paths to tumah is simply unavailable to it?
Rebbi Eliezer answered, "Lo shamati", I have not heard. He was not denying that such a garment requires hesger; his mesorah told him that it does. What he had not received from his rabbeim was the reason, and Rebbi Eliezer never offered a ruling in halachah that he had not heard from his teachers.
At this point Rebbi Yehudah ben Beseira offered, "Alamdenu bo", allow me to instruct you in it. He was requesting leave to provide a rationale for the transmitted halachah that a lone white band, already entirely discolored and with no room left for spreading, is nevertheless subject to hesger. Rebbi Eliezer's response laid down a condition: "Im lekayeim divrei chachamim, hein", meaning, yes, provided your explanation sustains what the chachamim ruled.
The proposal of Rebbi Yehudah ben Beseira was simple: "Shema ya'amod bo shenei shavuos, veha'omeid bebegadim shenei shavuos, tamei." It may be that the nega will hold steady for a fortnight, and a nega covering a gris or more in a garment that stays unchanged through two weeks makes the garment tamei, and it goes to the fire. Because that avenue to tumah remains entirely available in our case, hesger is required. Rebbi Eliezer answered him, "Chacham gadol attah, shekiyamta divrei chachamim", you are a great sage, for you have upheld the words of the chachamim.
The answer seems almost obvious, which invites the question of what the difficulty was in the first place. Apparently the assumption behind the question was that in order for a garment to enter the framework of hesger, it should have to be capable of both forms of tumah, standing unchanged for two weeks and also spreading. If only one of the two can ever apply, perhaps the garment falls outside the parshah of nega'im altogether. Rebbi Eliezer's mesorah told him otherwise, but without a reason. Rebbi Yehudah ben Beseira showed him that there is no basis for such a distinction: the capacity to remain for two weeks and thereby require burning is by itself enough to obligate hesger, even where pisyon is impossible.
The shiur of pisyon
Three measures round out the mishnah. "Hapisyon hasamuch, kolshehu": where the growth breaks out right beside the original nega (the om), no minimum applies; even the slightest enlargement of the om suffices.
"Harachok, kegris": where the fresh discoloration surfaces away from the om, say on the far side of the cloth, or a band or two over in the striped kaita we have been discussing, it qualifies as pisyon only if it measures a gris on its own.
"Vehachozeir, kegris": an identical measure governs a nega that comes back. The case is one where the nega had shrunk, the discolored section was cut away and a patch (matlis) was stitched into the opening, after which the nega surfaced once more, either on the patch or somewhere else on the garment. Here too, the returning nega qualifies only if it covers a gris.