Talmud for Kelim 8:10
מַגַּע טְמֵא מֵת, שֶׁהָיוּ אֳכָלִין וּמַשְׁקִין לְתוֹךְ פִּיו, הִכְנִיס רֹאשׁוֹ לַאֲוִיר הַתַּנּוּר טָהוֹר, טִמְּאוּהוּ. וְטָהוֹר שֶׁהָיוּ אֳכָלִין וּמַשְׁקִין לְתוֹךְ פִּיו וְהִכְנִיס רֹאשׁוֹ לַאֲוִיר הַתַּנּוּר טָמֵא, נִטְמָאוּ. הָיָה אוֹכֵל דְּבֵלָה בְיָדַיִם מְסֹאָבוֹת, הִכְנִיס יָדוֹ לְתוֹךְ פִּיו לִטֹּל אֶת הַצְּרוֹר, רַבִּי מֵאִיר מְטַמֵּא, רַבִּי יְהוּדָה מְטַהֵר. רַבִּי יוֹסֵי אוֹמֵר, אִם הָפַךְ, טָמֵא. אִם לֹא הָפַךְ, טָהוֹר. הָיָה פֻנְדְּיוֹן לְתוֹךְ פִּיו, רַבִּי יוֹסֵי אוֹמֵר, אִם לִצְמָאוֹ, טָמֵא:
If a person who came in contact with one who has contracted corpse impurity had food or liquids in his mouth, and he put his head into the air-space of an oven that was pure, they cause the oven to become impure. If a person who was ritually pure had food or liquids in his mouth, and he put his head into the air-space of an oven that was impure, [the food and drink] become impure. If a person was eating a pressed fig with impure hands, and he put his hand into his mouth to remove a small stone: Rabbi Meir declares [the fig] to be impure. But Rabbi Yehudah declares it pure. Rabbi Yose says: If he turned it over [in his mouth] it [the fig] is impure, but if he did not turn it over [the fig] is pure. If the person had a coin in his mouth, Rabbi Yose says: if he kept it there to relieve his thirst, it becomes impure.