Taharos, Chapter 4, Mishnah 5. Our chapter has been mapping out what to do with a safek tumah: when we rule tamei, when we rule tahor, and when the matter is left hanging. This Mishnah addresses a specific and delicate corner of that map: "Al shishah sefekos sorfin es haterumah", there are six cases of doubt on account of which terumah is burned.
Why is this delicate? Because with terumah there is very little middle ground. If terumah has become tamei, there is a mitzvah to burn it. If it has not become tamei, burning it is forbidden, since one may not destroy terumah that is still fit. A doubt would ordinarily leave us paralyzed, holding the terumah without eating it and without destroying it. Regarding these six sefekos, however, Chazal issued a gezeirah that the terumah is to be burned. Let us go through them.
The six cases
1. Safek beis haperas. A beis haperas is a field containing a grave that was plowed over. The plow turns the earth, and with it the contents of the grave, and now bones may have been dragged in any direction across the entire field. A small fragment of the skeleton could easily have been carried clear from one end to the other. If a person touched or carried a clod of earth from such a field and then came into contact with terumah, or the terumah itself came into contact with that earth, the terumah is burned.
2. Safek afar haba me'eretz ha'amim. The Chachamim decreed tumah upon the lands of the nations, on the assumption that a corpse may be buried anywhere in them. Those of us living outside Eretz Yisrael should know that we carry that status. Earth from chutz la'aretz therefore carries a safek tumah, and terumah involved with it is burned.
3. Safek bigdei am ha'aretz. The term am ha'aretz here does not simply describe an unschooled villager, or a person whose word we generally distrust. In this context it means someone who is lax about hilchos taharah. We assume his wife is no more scrupulous than he is, and it is entirely possible that she handled his clothing during her days of niddah. His garments therefore stand under a real suspicion of tumah, and terumah that may have come in contact with them is burned.
4. Safek kelim hanimtza'im. Vessels found lying about, whose owner and history are unknown. Perhaps a zav moved them or leaned on them; perhaps they were under the same roof as a corpse. That doubt, combined with the doubt about contact with terumah, is enough to require burning.
5. Safek rukin hanimtza'in. Spittle found in a public place. The saliva of a zav conveys tumah, and we cannot know whose this is. This applies specifically to human saliva, which is recognizably different from that of an animal.
6. Safek mei raglei adam discovered next to the urine of an animal. Why does the Mishnah pair them? Because seeing the two side by side is precisely what enables us to recognize which one came from a human being: the comparison between them gives it away. And urine of a human being may have come from a zav.
What exactly triggers the burning
So we know the six cases. What is striking is that the Mishnah's own Tannaim do not agree on what to do with them, and it closes with a three-way machlokes.
The anonymous first opinion: "Al vaday magan shehu safek tum'asan sorfin es haterumah". Only when the contact itself is certain do we burn. In each of these six cases the tumah is a matter of doubt; we know for a fact that the terumah touched the beis haperas earth, or the garment, or the spittle, but we do not know that the item was truly tamei. For that combination, certain contact with a doubtful tumah, Chazal decreed burning.
Rebbi Yosi goes further: "af al safek magan birshus hayachid", even when the contact itself is also in doubt, so long as the incident occurred in a reshus hayachid, the terumah is burned. In his view the gezeirah of Chazal reaches that far.
The Chachamim take a middle position: "birshus hayachid tolin uvirshus harabbim tehorin". Where the contact is uncertain and it happened in a private domain, the terumah is suspended: we neither burn it nor use it, and it is left in limbo. Where the uncertain contact occurred in a public domain, the terumah is tahor and remains permitted.
Six recurring doubts of daily life, then, and three views on how far Chazal's decree extends. Behind all of them stands the same tension with which we began: terumah that is tamei must be destroyed, terumah that is tahor must be preserved, and the Sages had to draw the line precisely.