(22) And when you reap the harvest of your land, you shall not wholly reap the corner of your field, you also shall not gather the gleaning of your harvest; you shall leave them for the poor, and for the stranger: I am Adonai your God.
(א) אלו דברים שאין להם שעור. הפאה, והבכורים, והראיון, וגמילות חסדים, ותלמוד תורה...
(ב) אין פוחתין לפאה מששים. ואף על פי שאמרו אין לפאה שעור, הכל לפי גודל השדה ולפי רוב העניים ולפי רוב הענוה.
(1) These are the things that have no measure: Peah [corner of the field which, while harvesting, must be left for the poor], Bikurim [First-fruits that must be brought to the Temple and given to the priest], the appearance-sacrifice [brought to the Temple on Pilgrimage Festivals], acts of kindness, and the study of the Torah...
(2) One should not make the Peah less than one-sixtieth [of the entire crop]. And although they [the Sages] say that there is no definite amount given for Peah, it is all based upon the size of the field and upon the number of poor [who will be collecting it] and upon the abundance of the crop.
(10) You shall not pick your vineyard bare, or gather the fallen fruit of your vineyard; you shall leave them for the poor and the stranger: I the LORD am your God.
(9) ולקט קצירך THE GLEANINGS OF THY HARVEST — Gleanings are ears that drop from the hand of the harvester during the reaping — one or two at a time, but three do not come under the category of לקט.
Maimonides on Pe'ah and Leket (Mishneh Torah: Gifts To the Poor)
1:8) With regard to all of these gifts to the poor, owners may not derive any benefit from them, but rather the poor come and take them regardless of the owner's wishes. Even if he [the farmer] is one of the poor of Israel, they take them from his possession.
2:12) One should only leave pe'ah from the end of one's field so that the poor know the place they are to go and so that it is known to the passers-by, so they will not suspect anything. This is so because there are liars who intend to harvest the whole field who could say to those who see him harvesting the end of the field, "I left my due from the beginning of the field." And moreover [this applies so] he will not wait until a time when no one is around and leaves [his due] to his poor relative. But, if he transgressed and left pe'ah from the beginning of the field or from the middle, this still counts toward [the total amount of] the pe'ah portion. However, he still needs to leave the rest [of his due] from the end of the field so as to fulfill the fitting measure of pe'ah after he has separated the first part.
4:12) One who does not permit the poor to glean or who permits one but prevents another or who assists one of them rather than another is considered a robber of the poor.
4:13) It is forbidden for a man to let loose a lion or something similar within his field so that the poor see it and flee.
(יט) כִּי תִקְצֹר קְצִירְךָ בְשָׂדֶךָ וְשָׁכַחְתָּ עֹמֶר בַּשָּׂדֶה לֹא תָשׁוּב לְקַחְתּוֹ לַגֵּר לַיָּתוֹם וְלָאַלְמָנָה יִהְיֶה לְמַעַן יְבָרֶכְךָ יקוק אֱלֹקֶיךָ בְּכֹל מַעֲשֵׂה יָדֶיךָ. (כ) כִּי תַחְבֹּט זֵיתְךָ לֹא תְפָאֵר אַחֲרֶיךָ לַגֵּר לַיָּתוֹם וְלָאַלְמָנָה יִהְיֶה. (כא) כִּי תִבְצֹר כַּרְמְךָ לֹא תְעוֹלֵל אַחֲרֶיךָ לַגֵּר לַיָּתוֹם וְלָאַלְמָנָה יִהְיֶה. (כב) וְזָכַרְתָּ כִּי עֶבֶד הָיִיתָ בְּאֶרֶץ מִצְרָיִם עַל כֵּן אָנֹכִי מְצַוְּךָ לַעֲשׂוֹת אֶת הַדָּבָר הַזֶּה.
(19) When you reap your harvest in your field, and have forgotten a sheaf in the field, you shall not go back to collect it; it shall be for the stranger, for the fatherless, and for the widow; that Adonai your God may bless you in all the work of your hands. (20) When you beat your olive-tree, you shall not go over the boughs again; it shall be for the stranger, for the fatherless, and for the widow. (21) When you gather the grapes of your vineyard, you shalt not glean it; it shall be for the stranger, for the fatherless, and for the widow. (22) And you shalt remember that you were a slave in the land of Egypt; therefore I command you to do this thing.
(14) And Boaz said unto her [Ruth] at meal-time: ‘Come, and eat of the bread, and dip your morsel in the vinegar.’ And she sat beside the reapers; . . ., and she did eat and was satisfied, and left. (15) And when she was risen up to glean, Boaz commanded his young men, saying: ‘Let her glean even among the sheaves, and put her not to shame. (16) And also pull out some for her of purpose from the bundles, and leave it, and let her glean, and don't rebuke her.’ (17) So she [Ruth] gleaned in the field until evening; and she beat out that which she had gleaned, and it was about an ephah of barley.