Positive commandment · Mitzvat Aseh #120 of 613
To leave pe'ah
להניח פיאה
The verse · Vayikra 19:10
וְכַרְמְךָ לֹא תְעוֹלֵל וּפֶרֶט כַּרְמְךָ לֹא תְלַקֵּט לֶעָנִי וְלַגֵּר תַּעֲזֹב אֹתָם אֲנִי ה׳ אֱלֹהֵיכֶם
“And thou shalt not glean thy vineyard, neither shalt thou gather the single grapes of thy vineyard; thou shalt leave them for the poor and stranger: I am the Lord your God.”
The Rambam’s words
To leave pe'ah.
להניח פיאה.
Why · Sefer HaChinuch #216
To leave over the corner of the field
“It is from the roots of the commandment that G-d, blessed be He, wanted that His people that He chose be crowned with every good and dear trait and that they would have a blessed soul and a generous spirit.”
Who & when
“And it is practiced by Torah writ by males and females — whether by Israelites, by Levites or by priests — specifically in the Land of Israel and at the time that Israel is there, as with the priestly tithe and the tithes.”
Where in the Mishneh Torah
Hilchot Heave Offerings הלכות תרומות