Tosefta for Yadayim 4:6
אוֹמְרִים צְדוֹקִים, קוֹבְלִין אָנוּ עֲלֵיכֶם, פְּרוּשִׁים, שֶׁאַתֶּם אוֹמְרִים, כִּתְבֵי הַקֹּדֶשׁ מְטַמְּאִין אֶת הַיָּדַיִם, וְסִפְרֵי הוֹמֵרִיס אֵינוֹ מְטַמֵּא אֶת הַיָּדַיִם. אָמַר רַבָּן יוֹחָנָן בֶּן זַכַּאי, וְכִי אֵין לָנוּ עַל הַפְּרוּשִׁים אֶלָּא זוֹ בִלְבָד. הֲרֵי הֵם אוֹמְרִים, עַצְמוֹת חֲמוֹר טְהוֹרִים וְעַצְמוֹת יוֹחָנָן כֹּהֵן גָּדוֹל טְמֵאִים. אָמְרוּ לוֹ, לְפִי חִבָּתָן הִיא טֻמְאָתָן, שֶׁלֹּא יַעֲשֶׂה אָדָם עַצְמוֹת אָבִיו וְאִמּוֹ תַּרְוָדוֹת. אָמַר לָהֶם, אַף כִּתְבֵי הַקֹּדֶשׁ לְפִי חִבָּתָן הִיא טֻמְאָתָן, וְסִפְרֵי הוֹמֵרִיס, שֶׁאֵינָן חֲבִיבִין, אֵינָן מְטַמְּאִין אֶת הַיָּדָיִם:
The Sadducees say: We denounce you, Pharisees! For you say that holy Scriptures render the hands impure, but the books of Homer [literally: Hameiras, i.e. secular books] do not render the hands impure. Rabban Yochanan ben Zakkai said "And is this alone all we have [to object to] over Pharisees? For they also say that the bones of a donkey are pure, but the bones of Yochanan the high priest are impure." They [the Sadducees] said to him, "In accordance with their love is their impurity, so that one does not fashion the bones of his father or his mother into spoons." He said to them, "So too regarding the sacred Scriptures; in accordance with their love is their impurity; and the books Homer, which are not beloved, do not render the hands impure."