Keilim, Chapter 16, Mishnah 4. This mishnah continues the chapter's theme of identifying the precise moment at which a vessel becomes a finished vessel. A raw material, or an item still under the craftsman's hand, is not yet a keli and cannot contract tumah. Only once the object can actually do the job it was made for does it enter the world of the laws of tumah and taharah. Here the Mishnah turns to items fashioned out of leather and asks, for each one, which final touch is the one that makes it usable.
The Mishnah opens with a general question: "Kelei or me'eimatai mekabelin tumah?" Leather vessels, from what point do they become susceptible to tumah? Four examples follow, and in each one the anonymous first opinion (the Tanna Kamma) and Rabbi Yehuda dispute where the line of completion falls.
The shepherd's bag
The first item is the turmal, a shepherd's satchel of the sort a person slung over his shoulder to carry provisions and other necessities while traveling. The Mishnah states: "Haturmal" is regarded as a keli "mi sheyachsos veyachnov," and, adds the first opinion, "veya'aseh kisotav." That is, the leather rim must be turned in and sewn down, the excess along the edge must be cut away evenly, and the cords must be run through the loops sewn around the opening so that the mouth can be pulled shut. Once that is done, whatever is placed inside stays inside, the satchel performs its function, and from that moment it belongs to the category of vessels that can become tamei.
Rabbi Yehuda sets the moment earlier: "mi sheya'aseh et oznav." For him it is enough that the loops themselves have been fashioned, and the cords need not yet have been drawn through them; with the loops in place the satchel can already be put to use. Since on his reckoning the bag reaches the status of a finished keli sooner, he is being stringent here, for susceptibility to tumah begins at that earlier stage.
The leather apron
The second item is the chartaya, a leather apron that laborers wore over their clothing while working. Its rule reads: "Vechurteya" is a keli "mi sheyachsos veyachnov," and the first opinion adds "veya'aseh et tzitzata." The craftsman must fold the leather edge back and sew it, cut the border straight, and fix on the pair of long straps joined at the apron's top ends, with which the wearer fastened the garment around himself. With those in place, the apron does exactly what an apron is meant to do.
Here too Rabbi Yehuda advances the moment of completion: "mi sheya'aseh et tab'oteha." The attaching of the rings suffices; the lengthy straps need not yet be tied on, because the apron can already be worn. And here as well his view is the more stringent of the two, since tumah takes hold from that earlier point.
The leather bedcover
"Ketavulya mi sheyachsos veyachnov." The katavlya was a leather cover spread over the frame of a bed to sleep on. The Tanna Kamma holds that it becomes a keli as soon as the craftsman has folded the edges over and stitched them down and trimmed the leather.
Rabbi Yehuda, however, requires more: "mi sheya'aseh et kichoteha." The cords must first be attached, those cords being sewn along the edges of the cover and then bound to the bedframe. To his mind they are precisely what enables the cover to serve its purpose, for once it is tied down it stays in place and does not slip about beneath the person lying on it; they are thus a genuine part of the article. Until they have been added, it cannot receive tumah at all.
The Tanna Kamma disagrees and holds that the cover already serves its purpose without the cords; they merely improve it. Notice that in this case Rabbi Yehuda is the more lenient of the two, since he requires one additional stage before the item counts as functional, which pushes the onset of susceptibility to tumah later.
The leather pillow and mattress
The final case is "Hakar vehakeset shel or," a cushion and a mattress fashioned from leather, whose rule is given as "mi sheyachsos veyachnov." In the view of the first opinion, they reach the status of a usable keli once the filling has been put in, the leather has been sewn closed around it, and the edges have been evened off.
"Rabbi Yehuda omer, mi sheyifrom veyashayer bahen pachot mechamishah tefachim." Rabbi Yehuda rules that they are already susceptible once the craftsman has done his sewing and left one side open with a gap of less than five tefachim, the opening through which the stuffing will be inserted. In other words, once three sides of the pillow are closed and only that small opening remains, the pillow is already fit to be used as a keli and can become tamei. The Tanna Kamma holds that it is not subject to tumah until it has been sewn completely shut. Here, then, Rabbi Yehuda is again the stricter opinion, since according to him the pillow enters the laws of tumah at an earlier stage than the Tanna Kamma would allow.
Across all four cases the underlying principle is the same: the halachah does not follow the craftsman's own sense of when he is finished, but asks a practical question, namely whether the object can already do what it was made to do. The disputes between Rabbi Yehuda and the Tanna Kamma are disagreements about that practical judgment, and depending on which item is under discussion, Rabbi Yehuda's assessment turns out sometimes stringent and sometimes lenient.