Peah, Chapter 4, Mishnah 4. This Mishnah too deals with the competition among the poor who come to gather the gifts designated for them.
The text of the Mishnah:
"Ein kotzrin osah b'magalos, v'ein okrin osah b'kardumos, kedei shelo yakeh ish es re'eihu"
"Ein kotzrin osah b'magalos" - the poor may not harvest the Peah with a sickle, that curved tool ordinarily used for cutting wheat.
"V'ein okrin osah b'kardumos" - nor may they uproot it with axes.
"Kedei shelo yakeh ish es re'eihu":
The situation could turn dangerous: when the poor are competing with one another, pushing and shoving, and a dangerous tool is in their hands, it could lead to a terrible accident, or even worse. Therefore the poor take the Peah with their hands alone, and in this way proper safety is maintained.
In summary: in this Mishnah we learned that Peah is gathered by hand and not with tools, neither with a sickle nor with an axe, out of concern that the poor, crowding against one another as they gather, might injure each other.