Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 210
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 210, with English translation by Maimonides (Rambam).
שלא לקצור כל השדה, שנאמר "לא תכלה פאת שדך בקוצרך" (ויקרא כג,כב).
Not to harvest one's entire field, as [Leviticus 23:22] states: "Do not completely harvest the ends of your fields."