Terumos, Chapter Seven, Mishnah Seven - the closing mishnah of the chapter, which continues the discussion opened in the two previous mishnayos. The case under discussion: we have before us two vessels, A and B. One of them contains Terumah and the other contains chullin, and we do not know which is which. Let us say we are dealing with wheat kernels, and one vessel holds Terumah wheat while the other holds chullin wheat. The mishnah addresses the question of what the law is when a person sows this wheat in his yard and it produces new wheat: may he eat the produce, or must he treat it as Terumah?
First background: one who sows definite Terumah:
Unintentionally - if he sowed it without knowing that it was Terumah, he is not permitted to benefit from whatever grows there, but he is permitted to work the land, to plow it and start over. It turns out that he gains nothing, but at least he can make use of his field.
Intentionally - if he deliberately sowed Terumah in his yard, he is penalized and is not even permitted to work the land. Rather, he must let the crop grow, and in the end treat it as Terumah and give it to a kohen. His loss is twofold: he does not benefit from the crop, and his land resource has also been drained to grow the kohen's wheat in his yard.
Second background: one who sows meduma:
With meduma, which is a mixture of chullin and Terumah, the rules are more lenient, and one must distinguish between types of seeds:
Something whose seed decomposes - a seed that rots and breaks down in the ground before the new plant grows out of it. Here the halachah is lenient, and what emerges from it is not treated as Terumah or as doubtful Terumah.
Something whose seed does not decompose - such as an onion or a clove of garlic, which remain in the ground with the plant emerging from them. Here the plant that emerges is treated as meduma, and it must be given to a kohen.
The ruling of the mishnah: sowing doubtful Terumah:
Our mishnah deals with a case of doubt - perhaps it is Terumah and perhaps it is meduma. "Zara es achas mehen" - a person took the seeds from vessel A, which are possibly Terumah and possibly chullin, and sowed them in his yard: "patur" - he is entirely exempt, since the kohen is the one seeking to extract from his fellow and the burden of proof is on him, and furthermore a doubt in a rabbinic law is resolved leniently. He need do nothing, and he may eat everything that grows from the ground.
"Vehasheniyah" - the second vessel, which was not sown: "noheg bah Terumah" - it is treated with the stringencies of Terumah, "vechayeves bechallah" - and challah is also separated from it if he made dough from the grain, since the stringencies of chullin apply to it as well, as was explained above. This is the opinion of Rabbi Meir, which is the anonymous opinion. "VeRabbi Yose poter" - Rabbi Yose follows his approach in the two previous mishnayos, that the status of vessel B is that of meduma, and a meduma mixture is exempt from separating challah, and therefore no challah is separated from vessel B at all.
"Zara acher es hasheniyah" - if a second person came and sowed the contents of vessel B in his yard, he too is "patur", and he may treat whatever grows in his yard as chullin. It turns out that each of them is judged on his own, and in each case we rule leniently, and his produce is completely exempt like any chullin.
"Zara echad es shteihen" - but if one person sowed the contents of both vessels, A and B, in his yard, then it is known with certainty that Terumah is growing somewhere in his yard. Therefore the same rules that apply to meduma itself apply here:
"Bedavar shezaro kaleh - mutar" - with seeds such as wheat, which break down completely in the ground before the new plant grows from them, he is permitted to eat all the wheat in his yard.
"Uvedavar she'ein zaro kaleh - asur" - with a plant whose seed does not break down completely before the new plant grows, such as an onion, the growths are forbidden and are treated as Terumah: he must give it all to a kohen, who will eat it with the stringencies of Terumah.
In summary: This mishnah, which concludes the chapter, deals with one who sows produce of doubtful Terumah status. One who sows one of the two containers is exempt, while the second is treated as Terumah and is obligated in challah according to Rabbi Meir, and Rabbi Yosi exempts it from challah because of its status as medumma (a mixture of Terumah and chullin). If a different person sowed the second container, he too is exempt, since each case is judged on its own leniently. But if one person sowed both of them, so that Terumah certainly grew in his field, the law is divided: with something whose seed disintegrates it is permitted, and with something whose seed does not disintegrate it is forbidden, and it is treated as Terumah.