Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 268
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 268, with English translation by Maimonides (Rambam).
שלא ייקח השכיר יתר על אכילתו, שנאמר "וְאָכַלְתָּ עֲנָבִים כְּנַפְשְׁךָ שָׂבְעֶךָ" (דברים כג, כה).
For a worker not to take more than what he eats [from the produce he harvests], as [Deuteronomy 23:25] states: "Do not put any into your receptacles."