Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 248
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 248, with English translation by Maimonides (Rambam).
שלא לכחש בממון חברו, שנאמר "לא תכחשו" (ויקרא יט,יא).
Not to deny [a just claim], as [Leviticus 19:11] states: "Do not deny your neighbor's [claim]."