Commentary for Eduyot 1:14
כְּלִי חֶרֶס מַצִּיל עַל הַכֹּל, כְּדִבְרֵי בֵית הִלֵּל. וּבֵית שַׁמַּאי אוֹמְרִים, אֵינוֹ מַצִּיל אֶלָּא עַל הָאֳכָלִין וְעַל הַמַּשְׁקִין וְעַל כְּלֵי חָרֶס. אָמְרוּ לָהֶם בֵּית הִלֵּל, מִפְּנֵי מָה. אָמְרוּ לָהֶם בֵּית שַׁמַּאי, מִפְּנֵי שֶׁהוּא טָמֵא עַל גַּב עַם הָאָרֶץ, וְאֵין כְּלִי טָמֵא חוֹצֵץ. אָמְרוּ לָהֶם בֵּית הִלֵּל, וַהֲלֹא טִהַרְתֶּם אֳכָלִים וּמַשְׁקִין שֶׁבְּתוֹכוֹ. אָמְרוּ לָהֶם בֵּית שַׁמַּאי, כְּשֶׁטִּהַרְנוּ אֳכָלִים וּמַשְׁקִין שֶׁבְּתוֹכוֹ, לְעַצְמוֹ טִהַרְנוּ. אֲבָל כְּשֶׁטִּהַרְתָּ אֶת הַכְּלִי, טִהַרְתָּ לְךָ וָלוֹ. חָזְרוּ בֵית הִלֵּל לְהוֹרוֹת כְּדִבְרֵי בֵית שַׁמָּאי:
An earthenware vessel [whose cover is (completely) fastened upon it] protects all that is in it (from tent-uncleanliness) according to Beth Hillel, [it being written (Numbers 19:15): "And every open vessel whose cover is not fastened upon it is unclean." But if its cover is fastened upon it, it and what is in it, whether vessels or food and drink, is clean. And the verse speaks of an earthenware vessel, it being written: "And every open vessel," connoting a vessel that contracts tumah through its opening and not through its back (i.e., an earthenware vessel).] And Beth Shammai say: It protects only food and drink and earthenware vessels (that are in it), [but not other vessels]. Beth Hillel asked them: Why? Beth Shammai answered: Because it (the earthenware vessel containing them) is tamei through an am ha'aretz (ignoramus) [For everything found with an am ha'aretz, both vessels and food and drink, are all in a status of tamei, because they are not versed in the halachoth of tumah and taharah, and think that what is tamei is tahor], and an unclean vessel does not intervene [i.e., it does not protect against tumah, but only a clean vessel does. An unclean vessel does not protect what is in it (from tent-uncleanliness). And the vessels of an am ha'aretz, since they are in a status of tamei, do not protect.] (At this,) Beth Hillel asked them: But did you not rule "tahor" the food and drink in it? Beth Shammai answered: When we ruled the food and drink in it "tahor," we did so for him, [the am ha'aretz himself. And we have no fear that a Torah scholar will come to use them, for they separate themselves from them. And even without this, all of their food is tamei. Therefore, as to food and drink and earthenware vessels, which cannot be purified in a mikveh, which were in the vessel of an am ha'aretz, whose cover was (completely) fastened — we tell them that they are tahor. And we have no fear that a Torah scholar will borrow from them and use them, for they are in the status of tamei to them and can never be made tahor. But with vessels that can be immersed (in a mikveh), we fear that a Torah scholar may borrow from them and use them without haza'ah (sprinkling the purification waters) on them the third and seventh days, not knowing that they had become tamei in a tent of the dead and thinking that immersion (in a mikveh) itself is sufficient for them, to free them of their tumah that they had contracted through the am ha'aretz], but when you (Beth Hillel) ruled the vessel "tahor," you did so for you and for him. [For a Torah scholar might come to use it. Therefore, they (Beth Shammai) ruled the same for all, that a vessel that could be immersed is not protected by a sealed covering, neither for a Torah scholar nor for an am ha'aretz. If they came to decree that the earthenware vessel of an am ha'aretz never "protects" (even) with a fastened cover, because it is in the status of tamei, the amei ha'aretz would never accept this, thinking that they are expert (in these laws) and that they keep their vessels tahor, and that their vessels "protect."] And Beth Hillel retracted, to rule in accordance with Beth Shammai.
Bartenura on Mishnah Eduyot
English Explanation of Mishnah Eduyot
But Beth Shammai says: “It protects only food and liquids and [other] vessels of earthenware.” Beth Hillel said to them: “Why?” Beth Shammai said to them: “Because it is [itself] impure with respect to an ignoramus, and no impure vessel can screen [against impurity].” Beth Hillel said to them: “And did you not pronounce pure the food and liquids inside it?” Beth Shammai said to them: “When we pronounced pure the food and liquids inside it, we pronounced them pure for him [the ignoramus] only, but when you pronounced the vessel pure you pronounced it pure for yourself and for him.”
Then Beth Hillel changed their mind and taught according to the opinion of Beth Shammai.
According to Numbers 19:15, a clay vessel that is covered with a lid prevents impurity from entering inside of it. If this vessel is found in a room with a dead body, which would normally cause everything in the room to be impure, the clay vessel and all that is inside of it does not contract the impurity. Beth Shammai and Beth Hillel argue about what types of things which may be inside the clay vessels are not impure. According to Beth Hillel any object inside the vessel is pure. Beth Shammai holds that only food, liquids and other clay vessels remain pure; non-clay vessels would be impure.
Beth Shammai explains that we can assume that the clay vessel has been touched by an ignoramus (am haaretz), a person who does not strictly know or observe the laws of ritual purity. It is assumed that the am haaretz makes the vessel impure. Since an impure vessel does not prevent the impurity from entering, the things inside of it are impure.
Beth Hillel responds to Beth Shammai by pointing out that they did indeed accept that the food and liquids inside the vessel were pure. If the clay vessel does not prevent impurity from entering, why should anything inside of it remain pure?
To this question Beth Shammai responds that when they stated that the food and liquids were pure they meant for the am haaretz himself and not for the haver (a person who scrupulously observes the laws of purity and indeed eats only pure food). Beth Shammai assumes that a haver will not borrow any of these things from an am haaretz, since they cannot be made pure (a clay vessel cannot be cleansed of its impurity). Therefore Beth Shammai can pronounce these things clean, knowing that they will never come into the hands of a haver. However, when Beth Hillel pronounced everything inside pure, they were in essence declaring it pure for both the am haaretz and the haver. Beth Hillel had implied that even metal vessels, inside the clay vessel, remained pure. A haver might borrow metal vessels from an am haaretz, with the intent of immersing them to cleanse them of their impurities. However, this immersion will only cleanse them from light impurities and not from impurity contracted from a dead body. Therefore, an am haaretz might borrow them thinking that he could cleanse them and in reality he could not. Due to this problem, Beth Hillel retracted their opinion and taught like Beth Shammai.