Demai, chapter seven, mishnah seven. This mishnah deals with produce of differing statuses that has become mixed together, and with the question of how terumas ma'aser can be separated from such a mixture with certainty. For the sake of the example we will speak of figs, and we will begin with several fundamentals without which the words of the mishnah cannot be understood.
Opening fundamentals:
From what is terumas ma'aser separated: Terumas ma'aser may be separated only from something that is actually ma'aser. It is not separated from something whose ma'aser and terumas ma'aser have already been taken. This is the decisive factor in every case in the mishnah.
What is the tevel of the mishnah: The tevel the mishnah is discussing is tevel whose terumah gedolah has already been separated - terumah is out of the picture. All that is lacking is ma'aser, and included within that potential ma'aser is also the portion of terumas ma'aser.
What is chullin: Chullin (mesukanim, properly tithed) means produce whose tithes have already been taken. It carries no obligation of ma'aser, and for that very reason it is entirely unfit for the separation of terumas ma'aser.
The difference between ma'aser and terumas ma'aser: The ma'aser is a monetary debt that the owner owes the Levi, and he may repay that debt in any manner he chooses, and he may even eat the produce itself - he is not required to give the Levi specifically those fruits that are the ma'aser. Terumas ma'aser, by contrast, may not be eaten by anyone who is not a kohen, and therefore the identity of whatever is ultimately designated as terumas ma'aser is of great consequence.
"Me'ah tevel u'me'ah chullin - notel me'ah ve'echad" - one hundred of tevel and one hundred of chullin: he takes one hundred and one:
One hundred figs of tevel require ten figs as ma'aser, and one of those ten is the terumas ma'aser given to the kohen. But once the hundred of tevel became mixed with the hundred of chullin, there is no way to identify what one is separating from.
The first hundred taken from the mixture might all be from the chullin, which carry no obligation of ma'aser and from which terumas ma'aser is not separated. Therefore the only way to be assured that at least one fruit was taken from the tevel - which is obligated in ma'aser, and that ma'aser is obligated in terumas ma'aser - is to take one fig beyond the hundred of chullin: one hundred and one figs. All of them must be treated as terumas ma'aser, and they may be eaten only by a kohen. Financially he may well be able to receive compensation for this, since in truth only one of them is actually terumas ma'aser.
"Me'ah tevel u'me'ah ma'aser - notel me'ah ve'echad" - one hundred of tevel and one hundred of ma'aser: he takes one hundred and one:
Here one hundred figs of tevel (of the type explained above) became mixed with one hundred figs that had been separated as ma'aser rishon. The reckoning of the obligation is as follows: the hundred of ma'aser require ten figs as terumas ma'aser, and the hundred of tevel require one fig. Out of the two hundred that are mixed together, then, eleven figs are needed for terumas ma'aser.
Taking eleven figs from the mixture is not enough, since they might all come from the tevel, and in one hundred figs of tevel there are only ten figs of potential ma'aser that can become terumas ma'aser, not eleven. He therefore takes one hundred and one figs, thereby ensuring that some were taken from the ma'aser as well, and all one hundred and one are treated as terumas ma'aser, to be eaten by a kohen alone.
"Me'ah chullin mesukanim u'me'ah ma'aser - notel me'ah va'eser" - one hundred of properly tithed chullin and one hundred of ma'aser: he takes one hundred and ten:
In this case one hundred figs of properly tithed chullin, from which terumos and ma'asros have already been separated and which carry no obligation of ma'aser at all, became mixed with one hundred figs of ma'aser, which require ten figs as terumas ma'aser.
Here one hundred and one is not enough; one must take one hundred and ten. The reason: the first hundred might all be from the properly tithed chullin, which carry no obligation of ma'aser and are unfit for terumas ma'aser. The only way to know with certainty that the ten figs come from the ma'aser and are fit to be considered terumas ma'aser is by taking one hundred and ten.
"Me'ah tevel v'tish'im ma'aser... lo hifsid klum" - one hundred of tevel and ninety of ma'aser... he has lost nothing:
The mishnah continues with a case in which one hundred figs of tevel became mixed with ninety figs of ma'aser. The hundred of tevel require ten as ma'aser, and one of those as terumas ma'aser; the ninety of ma'aser require nine figs as terumas ma'aser. All told, ten figs of terumas ma'aser are needed from the hundred and ninety.
In this case his position is far better: even if all ten figs he separates come from the tevel, there is no problem, for in one hundred figs of tevel there are ten that can be ma'aser, and all of them are therefore fit to become terumas ma'aser for the entire mixture. And likewise if they all come from the ninety of ma'aser, that too is valid, for all ninety are ma'aser, and terumas ma'aser may be taken from any kind of ma'aser.
This same ruling is stated in the mishnah regarding a similar case as well: ninety of tevel and eighty of ma'aser. That reckoning involves fractions, and we will set it aside, but the principle is identical to the case of one hundred of tevel and ninety of ma'aser.
In both of these cases "lo hifsid klum" - he has lost nothing: there is no need to separate more than the required measure. In the earlier cases there was no choice but to treat a far larger quantity as terumas ma'aser because of the doubt, whereas here he separates the actual required amount and knows with certainty that it comes from the ma'aser.
"Zeh ha'klal" - this is the rule:
The mishnah concludes: "Zeh ha'klal: kol zeman she'ha'tevel merubeh - lo hifsid klum" - this is the rule: whenever the tevel is greater than the ma'aser, the owner loses nothing. This rule is based on the final cases listed in the mishnah.
In summary: In this mishnah we learned three cases in which an enlarged separation is required because of the doubt - one hundred of tevel and one hundred of chullin (one hundred and one), one hundred of tevel and one hundred of ma'aser (one hundred and one), and one hundred of properly tithed chullin and one hundred of ma'aser (one hundred and ten) - and two cases in which the tevel is greater than the ma'aser and there is no loss at all. The principle common to them all: terumas ma'aser is separated only from that which is obligated in ma'aser, and therefore one must take a quantity that guarantees that the separation was certainly made from produce that carries the obligation.