Keilim, Chapter 3, Mishnah 2. This chapter deals with the size of the hole that renders an earthenware (cheres) vessel unusable, and thereby tahor, no longer able to receive tumah at all. The principle taught at the opening of the chapter was that a vessel designated for food becomes tahor once it is pierced with a hole through which an olive can pass, while a vessel designated for liquids becomes tahor when it can no longer hold its liquid. Our mishnah shows that the matter is not nearly as simple as it first appeared: the measure depends on what the particular vessel is used for, and that itself is the subject of a machloket.
The barrel: three opinions
"Hechavit, shiurah bigrogarot." So teaches Rebbi Shimon: an earthenware barrel is gauged by dried figs. As long as it can keep a dried fig from slipping through, it is still a vessel; once the breach has widened to the point where a dried fig would drop out, the barrel is tahor. Why figs? Because that is what people generally store in a barrel, and a dried fig is bulkier than an olive. It follows that an olive-sized opening leaves such a barrel entirely within the laws of tumah, and it goes on receiving tumah until the hole reaches a fig's dimensions.
Notice what Rebbi Shimon is doing. The earlier teaching gave a single flat measure for all food vessels, the size of an olive. Rebbi Shimon disputes that and introduces subjectivity into the ruling: each vessel is judged by the food it is actually meant to contain.
"Rebbi Yehuda omer: be'egozim." Rebbi Yehuda holds that a barrel is measured by walnuts. In his view the ordinary use of an earthenware barrel is to hold walnuts, which are larger still than dried figs. Accordingly, even a hole through which a dried fig would fall does not purify the barrel, since it can still serve for walnuts; only when the opening reaches the size of a walnut does the barrel become tahor from that point onward. Rebbi Yehuda is arguing directly with Rebbi Shimon about what barrels are normally used for.
"Rebbi Meir omer: bizeitim." For Rebbi Meir the measure of the earthenware vessel is the olive, precisely the standard given by the stam mishnah at the head of the chapter. As soon as an olive can pass through the breach, the barrel is tahor, and it makes no difference that dried figs and walnuts would still be retained inside.
Vessels used for both food and liquid
The opening of the chapter also established that a keli serving both solid food and liquid is judged lechumra, stringently, by the standard set for food vessels. Here the mishnah supplies the cases: "Halafes vehakedeirah, shiuran bizeitim." The ilpas, in which stew was cooked, and the kedeirah, the everyday cooking pot, are both gauged by the olive. A puncture too fine to retain liquid has already spoiled them for one of their functions, yet that does not purify them. Tumah continues to take hold of them until an olive can drop through the opening.
Which liquid sets the measure
"Rebbi Shimon omer: sheloshtan bezir'onim." Rebbi Shimon holds that seeds provide the measure for all three of these vessels. A narrow hole that lets the liquid trickle away leaves them tamei; only an opening through which seeds would fall renders them tahor. This follows from the rule stated earlier in the chapter: where a keli is used both for liquids and for solids, we go by the stricter, larger measure. Because these three are at times put to use for seeds, we do not release them from tumah the moment they cease to hold their liquid. We are stringent and treat them as still able to contract tumah for as long as seeds remain inside.
"Rebbi Shimon omer: sheloshtan bezir'onim." Rebbi Shimon rules that all three of these vessels are measured by seeds. A small hole that merely lets the liquid seep out does not purify them; only a hole large enough for seeds to fall through does. His reasoning follows the rule taught earlier: a vessel that serves both liquids and solids is judged lechumra, by the larger measure. Since all three of these vessels are at times pressed into service for seeds, we do not declare them tahor the moment they stop holding liquid. We rule strictly and keep them susceptible to tumah until they can no longer hold seeds.
The oil lamp
The mishnah now moves on to the lamp. Picture the earthenware lamp of those days: a small cheres receptacle with an aperture on its upper surface through which the oil was poured, and, projecting from its far side, a short nozzle in which the wick rested.
"Ner, shiuro beshemen." The measure of a lamp is oil: the moment the puncture prevents it from retaining its oil, it is tahor. "Rebbi Eliezer omer: bifrutah ketanah." Rebbi Eliezer sets the measure at a small perutah, since people would also keep small coins in a lamp. On his view the lamp remains susceptible to tumah so long as small coins cannot escape through the hole; only once they can does it turn tahor.
"Ner shenital piv, tahor." If the mouth of the lamp, the part from which the wick protrudes, broke away and was removed, the lamp is tahor. Without that spout it can no longer be called a lamp at all.
"Veshel adamah shehusak piv biftilah, tahor." Here is a lamp of clay that was never placed in a kiln, so it was never hardened and never brought to completion, and the only part of it that was ever baked is its mouth, fired by the burning of the wick. Such a lamp is tahor. The flame did indeed finish the mouth, but the body of the vessel was left unfinished, and so the lamp cannot receive tumah. Its gemar melachah, the act of completion that turns raw material into a genuine keli, has not taken place, and until it does the lamp lies entirely outside the laws of tumah.