Bava Metzia4: 9
אֵלּוּ דְבָרִים שֶׁאֵין לָהֶם אוֹנָאָה: הָעֲבָדִים, וְהַשְּׁטָרוֹת, וְהַקַּרְקָעוֹת, וְהַהֶקְדֵּשׁוֹת. אֵין לָהֶן תַשְׁלוּמֵי כֵפֶל, וְלֹא תַשְׁלוּמֵי אַרְבָּעָה וַחֲמִשָּׁה. שׁוֹמֵר חִנָּם אֵינוֹ נִשְׁבָּע, וְנוֹשֵׂא שָׂכָר אֵינוֹ מְשַׁלֵּם.  רַבִּי שִׁמְעוֹן אוֹמֵר: קָדָשִׁים שֶׁהוּא חַיָּב בְּאַחֲרָיוּתָן — יֵשׁ לָהֶן אוֹנָאָה; וְשֶׁאֵינוֹ חַיָּב בְּאַחֲרָיוּתָן — אֵין לָהֶן אוֹנָאָה. רַבִּי יְהוּדָה אוֹמֵר: אַף הַמּוֹכֵר סֵפֶר תּוֹרָה, בְּהֵמָה, וּמַרְגָּלִית — אֵין לָהֶם אוֹנָאָה. אָמְרוּ לוֹ: לֹא אָמְרוּ אֶלָּא אֶת אֵלּוּ.
The following things are not governed by [the law of] fraud: Slaves, deeds, land, and consecrated articles. [The rule of] two-fold payment does not [apply] to them, nor [that of] the fourfold and fivefold payment. An unpaid shomer need not take an oath, nor need a paid shomer pay.  R’ Shimon says: Consecrated articles for which one is responsible are governed by [the law of] fraud; but those for which he is not responsible are not governed by [the law of] fraud. R’ Yehudah says: Also one who sells a Torah scroll, an animal, or a pearl is not governed by [the law of] fraud. They said to him: They stated only these.