Keilim4: 4
[ד] כְּלִי חֶרֶשׂ שֶׁיֶּשׁ לוֹ שָׁלֹשׁ שְׂפָיוֹת, הַפְּנִימִית עוֹדֶפֶת — הַכֹּל טָהוֹר; הַחִיצוֹנָה עוֹדֶפֶת — הַכֹּל טָמֵא; הָאֶמְצָעִית עוֹדֶפֶת — מִמֶּנָּה וְלִפְנִים טָמֵא, מִמֶּנָּה וְלַחוּץ טָהוֹר. הָיוּ שָׁווֹת — רַבִּי יְהוּדָה אוֹמֵר: חוֹלְקִין הָאֶמְצָעִית. וַחֲכָמִים אוֹמְרִים: הַכֹּל טָהוֹר. כְּלֵי חֶרֶס מֵאֵימָתַי מְקַבְּלִין טֻמְאָה? מִשֶׁיִּצָּרְפוּ בַכִּבְשָׁן, וְהִיא גְמַר מְלַאכְתָּן.
An earthenware utensil that has three rims: [If] the inner one is higher, everything is tahor; [if] the outer one is higher, everything is tamei; [if] the middle one is higher, [then everything] from it and inward is tamei, [while everything] from it and outward is tahor. [If] they were even: R’ Yehudah says: We divide the middle [receptacle]. But the Sages say: Everything is tahor. From which point do earthenware utensils contract tumah? From when they are fired in the kiln, and this is the completion of their manufacture.