We now come to the ninth Mishnah in the fifth chapter of Maseches Terumos, the Mishnah that closes this fascinating chapter. Before we turn to the words of the Mishnah, let us begin with an illustration from everyday experience.
Anyone who has ever dug a hole in the sand at the beach knows that when you push the sand back into the hole, it does not all fit back in. The reason is that the sand has, as it were, grown while it was out of the hole: once it has been aerated, tiny gaps form between one grain and the next, the material becomes less compact, and it no longer fits back into its original place.
Conversely, material that was not compact and is then ground down has its tiny air pockets reduced, so that a far greater quantity fits into a small space. Coffee beans are a good example: their volume is large, and once they are ground, the volume of the ground coffee is far smaller than the volume of the original beans.
The question of the Mishnah:
What is the halachah when a person had the required ratio of one hundred parts of chullin against a single se'ah of Terumah, and after grinding the mixture the total volume decreased, so that he no longer has one hundred and one? Should we be concerned that what was lost was the chullin portion, while the Terumah remained at its original measure, so that there is no longer one hundred against one?
Put differently: perhaps the chullin was of lower quality, grain that was less compact, whether because it was infested or because it was not tightly packed, while the Terumah was of higher quality and more compact. If so, the ratio has changed, there is no longer one hundred against one, and the nullification does not take effect.
The Mishnah's answer is that we need not be concerned about this. We assume that things remained as they were, and that everything contracted and was ground and became denser in equal proportion, both the Terumah and the chullin. In the words of the Mishnah:
"Se'ah Terumah shenaflah leme'ah" - one unit of Terumah that fell into one hundred units of chullin.
"Utchanan" - he ground the one hundred and one units.
"Ufachasu" - and after the grinding he was left with less than one hundred and one, and there is room to be concerned that the ratio changed and the mixture became forbidden.
"Keshem shepachasu hachullin kach pachasah haTerumah" - just as the volume of the chullin was reduced, so too we may safely assume that the Terumah became denser in equal proportion, and the entire mixture remains permitted.
The reverse case:
What is the halachah when a person had less than one hundred units of chullin and one se'ah of Terumah fell into them, so that the mixture is forbidden, and after the grinding it turned out, remarkably, that the mixture yielded more than one hundred and one units? One might have said that what expanded was the chullin, which had been compact and became aerated, so that now there is one hundred against one and the mixture is permitted. But this is not so: we assume that just as the volume of the chullin grew, so too the Terumah expanded proportionally, and therefore the mixture remains forbidden.
When we know that the Terumah is of inferior quality:
Here, however, is something astonishing: if it is known that the wheat of the Terumah that fell was of lower quality, that is, less compact than the chullin, then during the grinding the volume of the Terumah will contract relative to the chullin, and in the end a ratio of one hundred parts chullin against one part Terumah will be created. In such a case a person is permitted to grind the mixture, and the mixture that results is permitted to be eaten.
The question of nullifying a prohibition intentionally:
Here a difficulty arises. We have a general rule that a person may not deliberately change the ratio in order to permit a mixture. For example: milk fell into chicken soup, and the soup contains only fifty times the amount of the milk. If he adds water or more soup in order to reach the measure of sixty times - it does not help, since this is deliberate nullification of a prohibition. The Mishnah itself states this explicitly at its conclusion.
If so, how was a person permitted to grind the mixture of Terumah and chullin, when he knows full well that since the chullin is denser than the Terumah, after the grinding a ratio of one hundred to one will be created and the mixture will become permitted?
The approach of Rabbeinu Ovadiah: This follows the opinion that one may nullify a prohibition intentionally. Rabbeinu Ovadiah permits a person to involve himself in the mixture deliberately, provided that he does not add additional chullin; but if he removes the forbidden substance, or as in our case, where he adds nothing at all but merely grinds, even though the ratio changes as a result - it is permitted.
An answer that is accepted as halachah according to all opinions: There is no cunning here whatsoever. Suppose it is clearly known that by volume there was not one hundred times the amount before the grinding, but by weight - the determining measure after the grinding - there indeed was one hundred times as much. What is a person to do with the forbidden mixture in his possession? He gives it to a kohen. And what will the kohen do with it? He will grind it, for that is the natural purpose of grain. Once it has been ground the ratio changes and the mixture becomes permitted, and the kohen can return it to its owner. It emerges that there is no need to give the mixture to a kohen at all, and a person may grind it himself at the outset, since this is not cunning but something that would have happened anyway.
This is the practical halachah in the body of the Mishnah: it is permitted to grind the mixture and there is no problem with doing so, provided it is known that by weight there was one hundred times as much chullin as Terumah. This is nothing more than grinding intended to set the volume ratios properly.
The conclusion of the Mishnah:
"Se'ah Terumah shenaflah lifchos mimeah" - one unit of Terumah that fell into fewer than one hundred units of chullin, and the mixture is forbidden as meduma.
"Ve'achar kach naflu sham chullin" - afterward additional chullin fell into it, and the scale tipped to one hundred units of chullin against one of Terumah.
"Im shogeg - mutar" - if the chullin fell in by mistake and not intentionally, the resulting mixture is permitted, since it contains one hundred times as much chullin as Terumah.
And if it was done intentionally - if he added chullin deliberately in order to change the ratio and render the mixture fit to be eaten, the mixture remains in its forbidden state.
In summary: In this Mishnah we learned that we are not concerned about a change in the ratio brought about by grinding - neither when the volume decreases nor when it increases - since we assume that the Terumah and the chullin changed in equal proportions; and that when it is known that the Terumah is of inferior quality and less dense, a person may grind at the outset until a ratio of one hundred to one is created, because this is not cunning but simply the natural course of the grain. We also learned the practical halachah that closes the Mishnah: a person may not add chullin deliberately in order to permit the mixture, and this halachah applies to mixtures of Terumah just as it applies to milk that fell into chicken soup and the like.