There is an obligation to leave the edge of the field for the poor. That is not to touch it at all. This is called "peah". The amount one must leave is 1/60.
That left over part is not obligated in the presents given to the priest or the Levite [called truma and maasar.]
Let's say however one just goes ahead and reaps the whole field. The second that he jumped the line and cut down the first stalk of the 1/60 the obligation of peah goes over to the sheaves. Some part of the sheaves he has to leave as peah so as to get up to 1/60 of the whole field.
But what happens to the first stalk of that started the process in the first place? and what happens to the second stalk of the 1/60 part that was the beginning of the transgression of the לא תכלה "Do not finish harvesting your field, but leave the corner of your field to the poor." Well the second he harvested that stalk, he transgressed that prohibition. So the questions are is the very first stalk still obligated in truma. (For at first it was obligated in truma since it is not "left over". But now all the reaped field is liable to be peah. Does that include the first stalk? And the difference is what is obligated in truma is called "tevel". Grain that has not had the presents to the priest and Levite separated rom it and thus forbidden to be eaten.) And what about the second stalk? Is it obligated in truma? For at first it was supposed to be peah. But the second he cuts it the obligation of peah goes over to the sheaves--but now it also is sheaf!! And it is peah? So which one is it?
