Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 212
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 212, with English translation by Maimonides (Rambam).
שלא לבצור עוללות הכרם, שנאמר "וכרמך לא תעולל" (ויקרא יט,י).
Not to harvest underdeveloped grape clusters, as [Leviticus 19:10] states: "Do not pick the incompletely formed grape clusters in your vine-yard."