Negaim, Chapter 2, Mishnah 5. This chapter is built around a single theme: the seeing of the Kohen, marei einei haKohen. A nega becomes tamei only when the Kohen actually sees it properly, and so the Mishnah has been laying down the conditions of a valid examination. Our Mishnah adds one more halacha of this kind, and it asks a practical question: keitzad re'iyas hanega, in what posture does the person stand while the Kohen looks him over?
The reason the posture matters is a basic rule of tzara'as. Only a nega on a part of the body that is exposed to view can bring tumas tzara'as. A spot located in a beis hasesarim, a concealed place of the body, does not make a person tamei. It follows that the examination must be conducted in a position that opens up the folds and creases of the body as much as they can naturally be opened, so that whatever ought to be seen is in fact seen.
The Position of a Man
"Ha'ish nireh ke'oder uche'mosek zeisim." A man is looked at while he holds himself the way a laborer holds himself when he works the soil with a hoe. Such a worker separates his feet and settles his weight between them, rather like a golfer setting up over the ball, and that spread of the legs uncovers the space between them. His arms, meanwhile, are held the way they are held by someone gathering olives from the tree. Since olive trees grow low, the picker reaches his fruit simply by raising his hands over his head, with no need to stretch himself unnaturally upward. That is precisely the limit the Mishnah has in mind: the arms go up only as far as an ordinary picker lifts them, and not higher.
A pleasant aside that you may recall from Zera'im: each of the four principal fruits has its own verb for harvesting. Grapes are botzer, one says botzer anavim. Olives are mosek, mosek zeisim, the very word our Mishnah uses. Dates are goder, goder temarim. Figs are oreh, oreh te'einim. Four fruits, four verbs.
The Position of a Woman
For a woman the Mishnah gives several postures, each one designed to reveal a different region of the body. First, "ke'oreches": she is seated on the ground as a woman sits when she is working her dough, kneading and arranging it for baking bread or cake. That seated working posture exposes what needs to be exposed below.
Second, "uchemeinikes es benah," as a woman nursing her child. This opens the area around the breasts, so that a nega there can be seen.
Third, the arms. Imagine a suspicious discoloration high on the arm, where the Kohen needs a clear view into the armpit, the shechi. For that the Mishnah has her stand "ke'oreges be'omeid," in the manner of a woman working at a standing loom, whose hand rises high as she passes her thread across the loom's upper beam and brings it back down again. Raising the arm that way opens the armpit to view. The Mishnah then limits this posture: "layad hayemanis," it serves for the right hand.
"Rebbi Yehuda omer, af keTovah befishtan lasmalis." Rebbi Yehuda adds the posture of a woman spinning flax thread, which serves for the left hand, since there too the arm is drawn upward and the armpit is exposed.
Is There a Machlokes Here?
The Tosfos Yom Tov raises a sharp point. The Rav (the Bartenura) offers no ruling here as to whether we follow Rebbi Yehuda, and such silence calls for an explanation. His suggestion is efshar lomar deTanna Kamma lo palig: perhaps there is no argument between them whatsoever. The first Tanna addressed the posture for one side of the body, the right, while Rebbi Yehuda supplies what is needed for the other side, the left, so that each statement fills in what the other left open. Ve'af al gav detani lah bilshon plugta, even though the Mishnah frames it as though it were a dispute, "the Tanna Kamma says... Rebbi Yehuda says...", such phrasing appears in many places without a real disagreement behind it, as he already demonstrated in the fourth perek of Bikkurim. And once there is no clash between the two Tannaim, the Rav had nothing to rule on and no cause to write ve'ein halacha keRebbi Yehuda.
He adds that the Rambam, too, left the matter unresolved in his Peirush HaMishnayos. Now our printed editions of the Rambam's commentary on Negaim do read ve'ein halacha keRebbi Yehuda, and this did not escape the Tosfos Yom Tov: he remarks that the older manuscripts of the Peirush contain those words, which is indeed the version in our hands. He then draws attention to the Rambam's Yad, Hilchos Tzara'as perek 9, where Rebbi Yehuda's posture is never mentioned. From that omission it emerges that the Rambam read the Mishnah as a real machlokes and decided in favor of the Tanna Kamma, the Chachamim: the loom stance is employed for the right hand only, and not for the left.
The Same Positions for the Shaving
The Mishnah's final clause carries the whole discussion one step further: "keshem shenireh lenega," and in the identical way, "kach hu nireh letiglachto." A metzora who had been ruled a muchlat and is now declared clean opens his taharah process with the tiglachas, at which all the hair of his body is removed. Every stance described above for the Kohen's inspection is assumed once more at that shaving, so that each region which had to be laid open to the Kohen's eye is equally reachable by the razor, leaving no hair in those spots untouched.