Pe'ah, Chapter 1, Mishnah 2. In the previous Mishnah we learned that Pe'ah has no fixed measure, no set amount. In the Mishnah before us we will see that the Sages did establish a minimum measure for it, and that even this measure is not fixed for all time but changes according to the circumstances.
The rabbinic measure of Pe'ah:
The Mishnah opens by ruling: "Ein pochasin la'pe'ah mi'shishim" - one does not give the poor less than one sixtieth of the field. This measure is not from the Torah but from the Sages, as the Mishnah itself stresses: "V'af al pi she'amru ein la'pe'ah shiur" - by Torah law it has no measure at all, while the Sages established that the one who gives may not give less than one sixtieth.
Three factors that determine the measure:
But even one sixtieth is not enough in every case, because there are additional factors to take into account, as the Mishnah puts it: "Hakol lefi godel hasadeh, u'lefi rov ha'aniyim, u'lefi rov ha'anavah".
"Lefi godel hasadeh" - everything depends on the area of the field and its size.
"U'lefi rov ha'aniyim" - according to the number of poor people and the extent of their need.
"U'lefi rov ha'anavah" - according to the blessing found in the crop.
How does this work in practice? When the field is large and the poor are few, the measure the Sages established is sufficient - one sixtieth. But when the field is small and the poor are many, and the need is great, one must add to the one sixtieth, so that the poor derive real benefit.
And as for the blessing: sometimes even a small field produces a large quantity of grain, all depending on the quality of that particular year. Someone who merited an abundant yield and blessing in his field, even if the poor are not many, is obligated to add to the measure and to give the poor with an open hand more than one sixtieth, corresponding to the blessing that the Holy One, Blessed is He, bestowed upon him.
In summary: although Pe'ah has no measure by Torah law, the Sages established that the one who gives may not give less than one sixtieth. This measure is only a floor, and the true amount is determined by three factors: the size of the field, the number of poor people, and the extent of the blessing in the crop - and according to them the owner of the field is obligated to add and to give generously.