Pe'ah, Chapter 1, Mishnah 6. This mishnah deals with the matter known as miru'ach hakri, the smoothing of the grain pile. Miru'ach hakri means leveling off the heap of grain after it has been gathered - a sort of final finishing touch given to the pile.
Miru'ach hakri carries special importance, since it is the dividing line from which the obligation to separate Terumah and ma'asros takes effect. Until that point a person may eat from the grain without Terumah and ma'asros in the manner of a casual snack, meaning an incidental eating that is not part of a meal. This dividing line stands at the center of our mishnah.
"Le'olam hu nosein mishum pe'ah ufatur min hama'asros ad sheyemare'ach" - A person may always give from his produce as pe'ah, and it is exempt from ma'asros, until he smooths the pile.
A person may give part of his produce as pe'ah, and it is exempt from ma'asros. As we have learned, whatever is given as pe'ah need not have Terumah and ma'asros separated from it - and this law applies only up until the time of the miru'ach.
Usually pe'ah is given while the crop is still standing in the field, long before the miru'ach. But if for some reason this was not done and the obligation of pe'ah still rests upon the owner, the pe'ah that he now gives is exempt from ma'asros even though the grain has already been harvested and winnowed, provided that the miru'ach has not yet been performed. Once the miru'ach has been performed, the grain has become obligated in Terumah and ma'asros, and even the pe'ah set aside for the poor man requires that Terumah and ma'asros be separated first, and only afterward is it given to the poor man. Some hold that in such a case the owner has caused the poor man a loss, since had he separated the pe'ah earlier he would not have had to separate Terumah and ma'asros from it, and therefore he owes the poor man that amount.
"Venosein mishum hefker ufatur min hama'asros ad sheyemare'ach" - And he gives as ownerless property, and it is exempt from ma'asros, until he smooths the pile.
As was mentioned, hefker, property that has no owner, is likewise exempt from ma'aser. This exemption too applies only until the miru'ach: once the miru'ach has been performed, even hefker is obligated in Terumah and ma'asros.
"Uma'achil labeheimah velachayah vela'ofos ufatur min hama'asros ad sheyemare'ach" - And he feeds domestic animals, wild animals and birds, and it is exempt from ma'asros, until he smooths the pile.
One may feed grain to a domestic animal, to a wild animal and to birds, and the one who feeds them is exempt from ma'asros - there is no obligation to separate Terumah and ma'asros before they eat. This allowance too applies only until the miru'ach; once the miru'ach has been performed, Terumah and ma'aser must be separated even before he feeds the animals and the birds.
One who takes grain for planting - the dispute between Rabbi Akiva and the Sages:
Rabbi Akiva: One who takes grain from the threshing floor, from the storehouse or from wherever it is stored in order to plant it is exempt from tithing it, and this holds until the miru'ach is performed. Rabbi Akiva too agrees that once the miru'ach has been performed, even if his intention is only to plant, he must first separate Terumah and ma'aser. This obligation is rabbinic, for by Torah law the verse says "and you shall eat," and the obligation applies to one who eats the grain and not to one who plants it.
The Sages: They disagree and hold that even before the miru'ach one must separate ma'aser before planting.
A kohen and a Levi who bought a threshing floor:
A kohen and a Levi who bought a threshing floor full of grain get to keep the gifts for themselves. They must separate Terumah and ma'aser, for otherwise the grain is tevel, but after the separation the kohen may keep the Terumah and the Levi may keep the ma'aser. This law too applies only until the miru'ach: if they bought the grain after the miru'ach was performed in it, they may not keep for themselves the Terumah and ma'aser that they separated, but must give them to another kohen and another Levi.
This penalty is a rabbinic enactment: the Sages did not want kohanim and Levi'im running to buy up other people's produce in order to gain the gifts, thereby harming those kohanim and Levi'im who cannot afford to buy and who are fit to receive the Terumah and the ma'aser.
One who consecrates his produce and redeems it:
One who consecrates his produce, making it holy and dedicated to the use of the Beis HaMikdash, and afterward redeems it, has an obligation that depends on the question of in whose hands the miru'ach was performed. If the treasurer, the officer who represents the funds of the Beis HaMikdash, is the one who performed the miru'ach, meaning that the miru'ach was done under the auspices of hekdesh, the produce is exempt from ma'asros. From here emerge three cases:
He consecrated it before the miru'ach, the miru'ach was performed under the hand of hekdesh, and afterward he redeemed it - exempt from ma'asros.
He consecrated it and redeemed it before the miru'ach, so that the miru'ach was not performed under the auspices of hekdesh - obligated in ma'asros.
He consecrated it after the miru'ach and redeemed it after the miru'ach, so that once again the miru'ach was not performed under the auspices of hekdesh - obligated in ma'asros.
In summary: In this mishnah we learned that miru'ach hakri is the dividing line that creates the obligation in Terumah and ma'asros. Until the miru'ach, pe'ah, hefker and feeding domestic animals, wild animals and birds are all exempt; according to Rabbi Akiva even one who takes grain for planting is exempt until the miru'ach, while the Sages disagree and obligate even before that. A kohen and a Levi who bought a threshing floor before the miru'ach keep the gifts for themselves, whereas those who buy after the miru'ach were penalized and must give them to another kohen and Levi. And one who consecrates his produce is exempt from ma'asros only when the miru'ach was performed while the grain was still under the auspices of hekdesh.