Keilim20: 4
עֲרֵיבָה גְדוֹלָה שֶׁנִּפְחֲתָה מִלְּקַבֵּל רִמּוֹנִים, וְהִתְקִינָהּ לִישִׁיבָה — רַבִּי עֲקִיבָא מְטַמֵּא, וַחֲכָמִים מְטַהֲרִין עַד שֶׁיְּקַצֵּעַ. עֲשָׂאָהּ אֵבוּס לַבְּהֵמָה, אַף עַל פִּי שֶׁקְּבָעָהּ בַּכֹּתֶל — טְמֵאָה.
[Regarding] a large trough that was [too] damaged to hold pomegranates, and one prepared it to sit on, R’ Akiva rules it tamei. But the Sages rule it tahor until one cuts [it]. [If] he made it into a manger, even if he set it in a wall, it is tamei.