“This is the statute of the Torah… [Concerning] the gold, silver, copper, iron, tin and lead [articles], any article that is used with fire, you shall process in fire and it will then become pure, but it shall [also] be purified with sprinkling water, and everything that is not used in fire you shall process in ritual water. ”
These pesukim are the source for the Gemarah Avodah Zarah (75b) to require the immersion of all eating utensils acquired from a non-Jew in a mikveh. The status of this requirement is undecided amongst the Rishonim. The Rambam does not include the immersion of eating utensils in his count of Mitzvot Aseh, nor does the Ramban mention it as a mitzvah that the Rambam omitted. Both seem to agree it is not a Mitzvat Aseh. Rashi on the other hand calls the immersing of eating utensils a “gzeirat hakatuv”, a decree of the Torah, indicating it is a biblical mitzvah. This is the opinion of Rav Yosef of Kurvil (1210 – 1280) in his Sefer Mitzvot Katan (sec.199) who counts dipping utensils acquired from non –Jews in a mikva as one of the 613 mitzvot.
If we are to accept the opinion that immersing these utensils is not a mitzvah, what is the status of this Halacha? One possibility is that it is only a Rabbinic requirement and the reference in the Gemarah to the pasuk is only an “asmachta”, a support, and not the literal teaching of the pasuk. Such an opinion is found in the KolBo (sec. 86) who states that the requirement to immerse the utensils in the Mikvah is only “midivrei Sofrim vesamchu al ma shekatuv”, of rabbinic origin who support themselves with the pasuk. The Kesef Mishneh suggests that this is the opinion of the Rambam who states in his Mishneh Torah (Maachalot Asurot 17/5): “Tevilah zo shematbilin klei haseudah hanilkachim min ha’akum veachar kach yutru leachila veshtiya einan leinyan tuma vetaharah ela midivrei sofrim, veremez lah ‘kol davar asher yavo…’ ” – this immersion of the eating utensils which are acquired from the gentiles and are then permitted for use of eating and drinking are not issues of impurity and purity only from (divrei sofrim) rabbinic decrees and an indication of this can be found in the pasuk…
On the other hand, the Rashba in his response (vol. 3 res. 255) suggests the Ramban sees the requirement to be a biblical requirement. The Lechem Mishneh explains that this is a function of the question, how to understand the term “Divrei Sofrim”, in the Rambam. According to the Lechem Mishneh, the Rashba understands it as a “Halacha leMoshe miSinai”, a decree taught to Moshe which is not written in the Torah. The halachik status of such a halacha is equivalent to a biblical law. Yet, since it is a Halacha leMoshe miSinai it would not be counted amongst the 613 mitzvot.
Rav Asher Weise in his Minchat Asher on Bamidbar (sec.68) suggests that the Rambam may have seen the act not as a commandment, either biblical or rabbinic, but rather as a “matir”, an act that comes to make something permissible. The act of immersion is meant to be “matir” the use of utensils that originate from gentiles. This means it could be biblical in origin yet, since it is not a commandment, it would not be counted amongst the 613 mitzvot. Rav Weise shows that the Rambam repeatedly uses the term “mutrim” become permitted. In Halacha 3, the Rambam speaks of new utensils bought from a gentile stating: “He who acquires eating utensils from a gentile whether of metal or glass which have not been used immerses them in the water of a Mikveh and then they will be permitted to be used”. Again, in the fifth halacha: “This immersion which we immerse eating utensils taken from the non-Jews and then they will be permitted to eat and drink…”
A possible consequence of the question whether immersion of utensils acquired from gentiles is a commandment or just a “matir” could be keeping non immersed utensils in one’s possession. If we see the requirement to immerse the utensils as a commandment then, regardless of intention to use, they must be immersed in a Mikvah. On the other hand, if the halacha is only a “matir” then, if there is no intent of use, there is no need to permit (be matir) the use of the utensil. One could argue against this distinction claiming that even if it is an independent mitzvah the requirement of the mitzvah applies only when there is intent to use the utensil.