Reference for Sheviit 4:1
בָּרִאשׁוֹנָה הָיוּ אוֹמְרִים, מְלַקֵּט אָדָם עֵצִים וַאֲבָנִים וַעֲשָׂבִים מִתּוֹךְ שֶׁלּוֹ, כְּדֶרֶךְ שֶׁהוּא מְלַקֵּט מִתּוֹךְ שֶׁל חֲבֵרוֹ, אֶת הַגַּס הַגָּס. מִשֶּׁרַבּוּ עוֹבְרֵי עֲבֵרָה, הִתְקִינוּ שֶׁיְּהֵא זֶה מְלַקֵּט מִתּוֹךְ שֶׁל זֶה, וְזֶה מְלַקֵּט מִתּוֹךְ שֶׁל זֶה, שֶׁלֹּא בְטוֹבָה, וְאֵין צָרִיךְ לוֹמַר שֶׁיְּקַצֵּץ לָהֶם מְזוֹנוֹת:
Originally it was said, one may collect sticks, stones and grasses from one's own field, just like one may collect from one's neighbor's field - the biggest items. Once transgressors multiplied, it was instituted that this one may [only] collect from that one's [field], while this one may collect [only] from that one's [field]; this mustn't be done as a favor, and it doesn't require mentioning that [one must not] stipulate to [give] them food [in exchange].