Those with less-observant friends and relatives have likely been invited to a home where the utensils have not been toveled. While food that is cooked or prepared in non-toveled keilim is clearly kosher (Tosefta, Avodah Zarah 8:2), using non-toveled keilim to eat this food may not be.
The permissibility of using these utensils may depend on how, precisely, one understands the requirement of tevilat keilim. The Rambam sees it as a metaphysical kashering (Hilchot Ma’achalot Asurot 17:3-6) – just as hag‘alah (boiling) or libbun (heating) permits one to use a treif utensil, so too tevilah permits one to use a utensil acquired from a non-Jew. Thus, according to the Rambam, utilizing non-toveled keilim is categorically forbidden.[i]
In other words, the Rambam does not consider tevilat keilim a mitzvah (an obligation per se), but a mattir (a prerequisite). For this reason, the Rambam prescribes no beracha for tevilat keilim, just as none is recited before kashering (several other Rishonim agree, see R. M.M. Karp, Mishmeret HaBayit, ch. 1 n. 3).
The accepted halacha, however, is that one does recite a blessing, at least in cases where tevilat keilim is undoubtedly required (Yoreh De‘ah 120:3). Apparently, normative halacha sees this precept as a mitzvah. If so, perhaps one may use someone else’s non-toveled utensils since the obligation to immerse them is fundamentally the owner’s, not the guest’s.
While this logic is appealing in theory, the Shulchan Aruch seemingly rejects it. Following earlier authorities, the Shulchan Aruch states that one who borrows a non-toveled utensil may not use it unless it is immersed (Yoreh De‘ah 120:8). Apparently, the obligation to tovel an item also falls upon anyone who wishes to use it.
However, Rabbi Yitzchak Isaac Liebes argues that the Shulchan Aruch actually presents no impediment to a guest using non-toveled utensils (Responsa Beit Avi 1:116). He writes that a guest is not properly consider a “borrower” since he does not care which particular dishes the host provides him and would not be expected to pay if any damage occurred to them.
Rabbi Liebes’ contention is debatable; the Shulchan Aruch could very well mean “borrower” not in the narrow sense, but as a generic term to cover anyone other than the owner of the utensil. But we can perhaps be more receptive to Rabbi Liebes’ chiddush in light of the fact that some Rishonim deny the very premise that using a kli prior to its immersion is forbidden (see, for example, Ra’aviya, Pesachim 464 and Rid, Avodah Zarah 75b). Granted, this position is difficult and only advanced by an extreme minority, but it can serve as supporting grounds for leniency if a guest is stuck (Mishmeret HaBayit ch. 1 n. 7 and n. 10).
An additional consideration for leniency is the principle of kevod ha’briyot. Many rabbinical restrictions are lifted if an affront to basic human dignity would otherwise result. According to many Rishonim, tevilat keilim is de’rabbanan; thus, there might be room to waive the requirement if refraining from using one’s host’s dishes would cause offense or embarrassment. However, the opinion that immersion is de’oraita is more commonly accepted as normative, at least for metal utensils (Bei’ur HaGra, Yoreh De‘ah 120:36). As such, a dispensation for kevod ha’briyot would seem to be inoperative.
However, several Acharonim rule that even if tevilat keilim is biblically required, the prohibition to use a non-toveled item is only de’rabbanan (see R. Tzvi Cohen, Tevilat Keilim: Halachot uMinhagim haShalem ch. 4 n. 2). If so, kevod ha’briyot would apply. It should be noted, though, that this ruling is quite novel; in fact, some Rishonim explicitly disagree with it. Nevertheless, kevod ha’briyot could certainly enter the equation when it comes to glass utensils, which most poskim say only need to be toveled due to a rabbinic injunction.
As a final consideration, we might add that some poskim maintain that the requirement of tevilah for utensils produced and sold by corporations is somewhat uncertain. These authorities rule that the vast majority of keilim nowadays should be toveled without a berachah since they have never been in the private possession of a non-Jew.[ii] This position can further bolster leniency vis-à-vis a guest in someone else’s home.
The bottom line: If one is invited to eat in a home where the keilim aren’t toveled, one should ask to be provided with utensils made of materials that are not subject to the requirement of tevilah, such as plastic.[iii] If this request would cause great awkwardness or discomfort, one can arguably use the host’s regular utensils. However, one should be hesitant to employ this leniency. According to the most straightforward understanding of halacha, it is forbidden to use any non-toveled utensil.
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[i] A possible exception to this would be eating non-liquid food from a non-toveled plate, which may not truly be considered “using” the plate since a plate is not necessary for eating a piece of cake the same way a bowl is necessary for eating soup, for example (Igrot Moshe, Yoreh De‘ah 3:22).
[ii] Rav Hershel Schachter rules this way since a corporation, as an independent legal entity, is neither Jewish nor non-Jewish. See also Mishmeret HaBayit 9:3.
[iii] A minority opinion requires plastic to be toveled, but even those who are personally stringent may certainly use non-immersed plastic utensils at another’s home. The same would apply to any other material that a legitimate halachic opinion exempts from tevilah.