Tevul Yom, Chapter 1, Mishnah 5. This masechta is devoted to a person who has already immersed in the mikvah during the day but must still wait for sunset before his taharah is complete. Earlier in the chapter we learned that the tumah carried by such a person, the tevul yom, is far weaker than the tumah of others who are tamei. Now that principle is brought to a concrete case: tiny grains and seeds clinging to the crust of a bread. When a tamei person lays his hand on one of those seeds, has he thereby touched the bread, or only a separate object that happens to be sitting there? Everything turns on whether the seed qualifies as food, and it is precisely on that question that the Tannaim divide.
The Mishnah opens with items that cannot really be eaten. "Hase'orah vehakusemes": barley and spelt, but only "bizman she'einan kelufim," so long as their husks have not been removed. Added to them are "vehati'ah vehachiltis veha'alum," three exceedingly hard species called ti'ah, chiltis and alum. To this group Rebbi Yehudah appends another item: "Rebbi Yehudah omer, af afunim shechorim," black beans belong here too.
About all of these Rebbi Meir rules leniently. The Mishnah states that they are "tehorim be'av hatumah," they remain tahor even where the one who touched them is an av hatumah, among the gravest grades of tumah at all, "ve'ein tzorech lomar betevul yom": the case of a tevul yom need not even be mentioned. So concludes the Mishnah: "divrei Rebbi Meir." The logic is straightforward. An item that no one would eat is not viewed as attached to the bread, it is not mechubar to it. Hence a hand of an av hatumah placed on such a seed lying on the crust brings no tumah to the bread at all, and where the toucher is merely a tevul yom, whose tumah is lighter yet, the conclusion needs no arguing.
The Chachamim disagree: "vachachamim omrim, tehorim betevul yom utemei'im bechol hatum'os." In their view the leniency is limited to the tevul yom alone. When a tevul yom touches these inedible seeds, the loaf beneath them stays tahor. But when a person with any other form of tumah touches them, the tumah does pass through to the loaf of bread.
Next come items that truly are foodstuffs. "Hase'orah vehakusemes bizman shehem kelufim": barley and spelt once their husks have been taken off. Then "vehachitah," a kernel of wheat, and here no distinction is drawn, "bein shehi kelufah," husked, "bein she'einah kelufah," unhusked. The list continues, "vehaketzach vehashumshum vehapilpel," ketzach, sesame and pepper, and Rebbi Yehudah supplements it: "Rebbi Yehudah omer, af afunim levanim," white beans as well.
Their halachah is the reverse: "temei'im betevul yom," and there is no need to spell out the ruling "bechol hatum'os." Being genuine edibles, these grains and seeds are regarded as part of the very bread they adhere to. Tumah therefore travels into the loaf even when the one who touched the seed is only a tevul yom, and where the toucher bears one of the weightier forms of tumah the bread is surely tamei, a conclusion the Mishnah leaves unstated.
The lesson of the mishnah is that the question of connection turns on edibility. A hard, unpeeled kernel or a bitter, inedible seed remains a foreign object resting on the bread; a peeled grain, a sesame seed or a peppercorn becomes part of the food itself, and whatever touches it has touched the loaf.