Reference for Bava Metzia 4:10
כְּשֵׁם שֶׁאוֹנָאָה בְמִקָּח וּמִמְכָּר, כָּךְ אוֹנָאָה בִדְבָרִים. לֹא יֹאמַר לוֹ בְּכַמָּה חֵפֶץ זֶה, וְהוּא אֵינוֹ רוֹצֶה לִקַּח. אִם הָיָה בַעַל תְּשׁוּבָה, לֹא יֹאמַר לוֹ זְכֹר מַעֲשֶׂיךָ הָרִאשׁוֹנִים. אִם הוּא בֶן גֵּרִים, לֹא יֹאמַר לוֹ זְכֹר מַעֲשֵׂה אֲבוֹתֶיךָ, שֶׁנֶּאֱמַר (שמות כב) וְגֵר לֹא תוֹנֶה וְלֹא תִלְחָצֶנּוּ:
Just as there is ona'ah in buying and selling, so there is ona'ah in words, [it being written (Leviticus 25:17): "And you shall not wrong, one man his fellow, and you shall fear your G d." This speaks of verbal wronging, the good or evil intent of one's words not being manifest, but known only to the speaker.] One should not ask another the price of an article if he does not intend to buy it. If he were a penitent, he should not say to him: "Remember your past deeds." If he were the descendant of proselytes, he should not say to him: "Remember the deeds of your ancestors," as it is written (Exodus 22:20): "And a stranger you shall not wrong, and you shall not oppress him."