אָסוּר לַמּוֹכֵר אוֹ לַקּוֹנֶה לְהוֹנוֹת אֶת חֲבֵרוֹ שֶׁנֶּאֱמַר (ויקרא כה יד) "וְכִי תִמְכְּרוּ מִמְכָּר לַעֲמִיתֶךָ אוֹ קָנֹה מִיַּד עֲמִיתֶךָ אַל תּוֹנוּ". וְאַף עַל פִּי שֶׁהוּא עוֹבֵר בְּלֹא תַּעֲשֶׂה אֵינוֹ לוֹקֶה מִפְּנֵי שֶׁנִּתָּן לְהִשָּׁבוֹן. וּבֵין שֶׁהוֹנָה בְּמֵזִיד בֵּין שֶׁלֹּא יָדַע שֶׁיֵּשׁ בְּמֶכֶר זֶה הוֹנָיָה חַיָּב לְשַׁלֵּם:
It is forbidden for a seller or a purchaser to take unfair advantage of a colleague, as Leviticus 25:14 states: "When you sell an entity to your colleague or purchase an entity from a colleague, one man should not take unfair advantage of his brother." Even though such a person transgresses a negative commandment, he is not punished by lashes, because the funds can be returned. Whether the person intentionally deceived his colleague or did not know that this transaction involved taking unfair advantage, he is obligated to pay the unwarranted gain.
