Quotation for Bava Metzia 116:16

Behold here we have [issues related] to monetary laws and laws of exploitation. And the latter is primary, since he in any case verbally exploited his fellow. And our Sages, may their memory be blessed, said in Bava Metzia 58b regarding the parameters of the negative commandment, “Do not exploit,” “If donkey drivers are asking to purchase grain from someone, and he has none, he may not say to them: Go to so-and-so, as he sells grain, if he knows about him that he never sold grain at all.” And the Shulchan Aruch, Choshen Mishpat 228:4 rules [like this]. And the Sages, may their memory be blessed, said with precision that one who said [this] to donkey drivers who regardless had come to a city to purchase grain, so no loss was caused to them, except that they requested that he inform them who sells [grain] and he mocked them with his words - violates the negative commandment of “Do not exploit.” And they judged accordingly in the beginning of Pesachim 3b about the Aramean who came up [and tricked the Jews] to eat from the Pesach sacrifices, etc. And Rabbi Yehuda ben Beteirah [who thwarted the Aramean’s trickery, by misleading him] knew that it was not considered mocking; otherwise he would have been in violation of “Do not exploit.” Here too, [even] had the rabbi, Rabbi Michael, lived in the village and the shochet mocked him to the point that he came to the synagogue to do the circumcision and found that there was no boy there to circumcise, he would have [still] violated this negative commandment. And our Sages were stringent about this over there, to the point that they likened it to worshiping idols (Bava Metzia 39a): “[There are] three [sins before whose transgressors] the curtain [between the world and the Divine Presence] is not locked (meaning, their sins reach the Divine Presence).”