Reference for Kelim 9:3
הַשֶּׁרֶץ שֶׁנִּמְצָא לְמַטָּה מִנְּחֻשְׁתּוֹ שֶׁל תַּנּוּר, טָהוֹר, שֶׁאֲנִי אוֹמֵר, חַי נָפַל וְעַכְשָׁיו מֵת. מַחַט אוֹ טַבַּעַת שֶׁנִּמְצְאוּ לְמַטָּה מִנְּחֻשְׁתּוֹ שֶׁל תַּנּוּר, טָהוֹר, שֶׁאֲנִי אוֹמֵר, שָׁם הָיוּ עַד שֶׁלֹּא בָא הַתַּנּוּר. נִמְצְאוּ בְאֵפֶר מִקְלֶה, טָמֵא, שֶׁאֵין לוֹ בַמֶּה יִתְלֶה:
If a <em>sheretz</em> [one of a number of small creatures which transmit impurity] is found beneath the bottom of an oven, the oven remains pure, for I can say that it fell there while it was still alive and that it died only now. If a needle or a ring is found beneath the bottom of an oven, the oven remains pure, for I can say that they were there before the oven arrived. If they were found in the wood ashes, the oven is impure since there is nothing upon which to base an assumption [of purity].