Reference for Kelim 6:2
הָאֶבֶן שֶׁהָיָה שׁוֹפֵת עָלֶיהָ וְעַל הַתַּנּוּר, עָלֶיהָ וְעַל הַכִּירָה, עָלֶיהָ וְעַל הַכֻּפָּח, טְמֵאָה. עָלֶיהָ וְעַל הָאֶבֶן, עָלֶיהָ וְעַל הַסֶּלַע, עָלֶיהָ וְעַל הַכֹּתֶל, טְהוֹרָה. וְזוֹ הָיְתָה כִּירַת הַנְּזִירִים שֶׁבִּירוּשָׁלַיִם, שֶׁכְּנֶגֶד הַסָּלַע. כִּירַת הַטַּבָּחִים, בִּזְמַן שֶׁהוּא נוֹתֵן אֶבֶן בְּצַד אֶבֶן, נִטְמֵאת אַחַת מֵהֶן, לֹא נִטְמְאוּ כֻלָּן:
A stone on which he placed [a pot] on it and on an oven, or on it and on a double stove, or on it and on a stove, is susceptible to impurity. [If he set the pot] on it and on another stone, on it and on a rock, or on it and on a wall, it is not susceptible to impurity. And such was the stove of the Nazirites in Jerusalem which was set up against a rock. The stove of the butchers: when the stones are placed side by side, if one of the stoves contracted impurity, the others do not become impure.