Negative commandment · Lo Ta’aseh #248 of 613
Not to deny [a just claim]
שלא לכחש בממון חברו
The verse · Vayikra 19:11
לֹא תִּגְנֹבוּ וְלֹא־תְכַחֲשׁוּ וְלֹא־תְשַׁקְּרוּ אִישׁ בַּעֲמִיתוֹ
“You shall not steal, neither deal falsely, neither lie one to another.”
The Rambam’s words
Not to deny [a just claim], as [Leviticus 19:11] states: "Do not deny your neighbor's [claim]."
שלא לכחש בממון חברו, שנאמר "לא תכחשו" (ויקרא יט,יא).
Who & when
“And this prohibition is practiced in every place and at all times by males and females.”
Where in the Mishneh Torah
Hilchot Oaths הלכות שבועות