Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 234
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 234, with English translation by Maimonides (Rambam).
שלא יתבע העני בחובו כשיידע שהוא עני, ולא יצר לו, שנאמר "לא תהיה לו, כנושה" (שמות כב,כד).
Not to demand payment of a debt from a poor person when one knows that he is impoverished, nor to cause him grief, as [Exodus 22:24] states: "Do not behave like a creditor towards him."