Mishnayos Bava Metzia Perek 4 Mishnah 10

Just as there is a prohibition against exploitation [ona’a] in buying and selling, so is there ona’a in statements, i.e., verbal mistreatment. The mishna proceeds to cite examples of verbal mistreatment. One may not say to a seller: For how much are you selling this item, if he does not wish to purchase it. He thereby upsets the seller when the deal fails to materialize. The mishna lists other examples: If one is a penitent, another may not say to him: Remember your earlier deeds. If one is the child of converts, another may not say to him: Remember the deeds of your ancestors, as it is stated: “And a convert shall you neither mistreat, nor shall you oppress him” (Exodus 22:20).

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: