Metal or glass food vessels that are acquired from a non-Jew, require Tevilas Keilim – immersion in a Mikva. This applies even the Keilim are new and have never been used. The Gemara derives this from Parshas Matos, where Elazar instructs the soldiers how to Kasher the Keilim that they plundered in their war with Midian.
There is a dispute in the Rishonim – both the Halachic authorities and Torah commentaries, whether Tevilas Keilim is a Biblical obligation or whether it is a Rabbinic obligation and the Pasuk is merely an Asmachta (brought as a support). This refers to metal Keilim. Tevilas Keilim for glassware is Rabbinic according to all opinion. Whether Tevilas Keilim is considered Deoraisa or Derabbanan has implications on whether one may perform Tevilas Keilim on Shabbos or not.
Background
The Mishna presents a dispute between Beis Shammai and Beis Hillel whether an impure person may immerse in a Mikva on Shabbos. However, they both concur that one may not immerse Keilim that were impure in a Mikva on Shabbos. The same applies on Yomtov. The Gemara provides 4 reasons for this prohibition; Rabbah teaches that it is due to a concern that one may carry the vessels in a public domain and violate Shabbos. The Rabbis applied this decree even on Yomtov and even in places where there is an Eruv as a safeguard.
Rav Yosef taught that it is because of a concern that one may squeeze the water out of clothing that would be immersed. The Rabbis applied their decree to all Keilim, even where there is no concern of squeezing.
Rav Bivi taught that the sages were concerned that one would leave their Toiveling to do on Shabbos or Yomtov when they would have more free time. The concern is that they may unintentionally use the Keilim for Terumah in the interim, before they were immersed.
Rava explains that the prohibition is because immersing a vessel to purify it makes the vessel useable and as such resembles the act “fixing a vessel”, which is a Biblical prohibition.
This discussion in the Gemara refers to immersing Keilim to purify them from Tumah. The Rishonim discuss whether the same concern applies to Tevilas Keilim for vessels that were acquired from a non-Jew. The answer depends on what is the reason for not immersing Keilim that were impure.
The concern of squeezing only applies to clothing and would not apply to food vessels, which only require immersion if they are made of metal or glass. Likewise, the concern of delaying immersing would not apply, because even if one inadvertently used the Keilim before immersing them, the food would remain Kosher.
However, the concern of carrying would still be applicable. The concern of resembling “fixing a vessel” would also apply to Tevilas Keilim which renders them useable.
The Rif only brings the reasons of Rav Bivi and Rav Yosef. Therefore, he would permit Tevilas Keilim on Shabbos. The Rambam also rules that Tevilas Keilim may be performed on Shabbos.
However, many Rishonim rule that one may not immerse Keilim on Shabbos. The Rosh writes that the primary reason is that of Rava. Based on this, he rules that one may not immerse new Keilim that were acquired from a non-Jew, on Shabbos or Yomtov. This is also the ruling of the Rashba.
The Shulchan Aruch brings both opinions, concluding that one who fears Heaven should be stringent. Rather than immersing the vessel, they should give it to a non-Jew as a gift and borrow it back to use on Shabbos.
Even though one may not give gifts or borrow on Shabbos, where the gift is for a Shabbos need such as in this case – to be able to use the vessel on Shabbos, borrowing or gifting is allowed.
After Shabbos one may technically leave the Keilim in the ownership of the non-Jew and continue to use them without Tevilah. Giving Keilim to a non-Jew to avoid having to immerse Keilim may even be done on a weekday.
However, the Ta”z writes that it is inappropriate to do this in an ongoing manner, and after Shabbos one should immerse the vessel in the Mikva. If it is still “borrowed” from the non-Jew one would not make a Bracha. If the non-Jew gives it back as a gift, it may be immersed with a Bracha. The Alter Rebbe and Mishna Berura rule like the Ta”z.
Further Exploration
The Gemara teaches that the prohibition of immersing Keilim on Yomtov only applies to vessels that have Biblical Tumah. A vessel that became impure with a Rabbinic Tumah may be immersed on Yomtov. Rashi explains that whereas purifying from Biblical Tumah resembles “fixing”, purifying from Rabbinic Tumah does not, since Biblically the vessel was considered pure.
The Maggid Mishna uses this to explain why the Rambam permits Tevilas Keilim on Shabbos. Since the Rambam rules that Tevilas Keilim is only Rabbinic, it is not considered a Tikkun. In contrast, the Rashba who is stringent, holds that immersing Keilim is a Biblical obligation. This is the opinion of the majority of Rishonim, including Rashi and Tosfos.
Based on this, even according to the stringent opinion, the prohibition of immersing Keilim on Shabbos should only apply to metal Keilim whose immersion is Biblically required. Since immersing glass Keilim is only a Rabbinic requirement, it should be permitted on Shabbos. The Rishonim do not mention this distinction.
Even though this distinction is not brought in the Rishonim, many Acharonim write that one may immerse glass Keilim on Shabbos. These include the Shaagas Aryeh, Pri Megadim and Panim Meiros. Other Poskim rule that Tevilas Keilim for glass is also prohibited on Shabbos. Their view is based on the Maggid Mishna.
The Maggid Mishna writes that the distinction in the Gemara between Tumah Deoraisa and Tumah Derabanan only applies for immersion for purification. This is because Keilim that are Tameh may technically be used for non-Terumah food. Therefore, we can be lenient on Shabbos to immerse Keilim that have only Rabbinic Tumah. This would not apply to Tevilas Keilim, even for glass, since we may not use vessels acquired from a non-Jew that have not been Toiveled.
The Alter Rebbe references this Maggid Mishna and writes that even according to those who hold that Tevilas Keilim is only Rabbinic, it could still be considered a Tikkun and thus forbidden on Shabbos. As such, it should apply to glass as well. The Mishna Berura is also stringent with glass Keilim.
The Alter Rebbe rules that since the Ikar is like the view that Tevilas Keilim is Mideoraisa, it may not be performed on Shabbos.
If one did immerse on Shabbos, the Alter Rebbe rules that the Keilim may still be used. In this case we rely on the lenient opinion which permits Tevilas Keilim on Shabbos. This ruling is based on the Magen Avraham, however the Magen Avraham does not write it with certainty, but rather “perhaps”.
In contrast to the Alter Rebbe, the Tzemach Tzedek writes that on Shabbos one may only be lenient if the vessels were immersed unknowingly. If it was done intentionally on Shabbos, one may not use them.
Where there is a doubt whether Tevilas Keilim is required at all, the Mishna Berura writes that one may rely on the lenient opinion to immerse them on Shabbos. However, the Ketzos Hashulchan argues with this leniency.
