Not to take a millstone as a pledge, as it is essential for sustenance

He prohibited us from taking in pawn, vessels with which people prepare their food, such as tools for grinding, kneading and cooking and tools for the slaughter of animals and other ones besides this that are grouped by the name, 'something with which food of sustenance (okhel nefesh) is made' - as it is stated, "for it is a soul that he takes in pledge" (Deuteronomy 24:6). And it remains for us here to explain their saying (Bava Metzia 115a), "And he is liable on account of two vessels, as it is stated, 'One shall not take as a pledge, a lower millstone nor an upper millstone.'" For this may make us think that they are two commandments - and all the more so, with their saying (Bava Metzia 116a), "And he is liable for the lower millstone on its own." And the content of this statement is that anyone who takes, as collateral, a vessel with which we make food of sustenance, transgresses a negative commandment, as it is explained; and one who takes several vessels - each one of which is used for food of sustenance - as collateral, is liable for each and every vessel. For example, if he takes as collateral, a tool for grinding, a tool for kneading and a tool for the making of bread. And this is something that does not need explanation; as it is like one who takes the garment of Reuven's widow as a pledge, and [likewise] the garment of Shimon's widow [and likewise the garment of Levi's widow] - that he transgresses for each and every garment. However the question is about one who takes as a pledge, two vessels with which, both together, he makes food of sustenance: Do we say that since the [specific preparation of] food is in fact only finished by both of them, the two of them are surely one vessel, and he should [only] be liable on account of one vessel; or since they are two vessels, he should be liable for each one on its own? And they explained to us that he is liable with them on account of two vessels - even though the work is done by bringing the two of them together, like a lower millstone and an upper millstone, as the grinding will not be done by one [of them] alone. And the language of the Mishnah is, "'One shall not take as a pledge, a lower millstone nor an upper millstone': Not only these did they say [is prohibited], but anything with which we make food of sustenance, as it is stated, 'for it is a soul that he takes in pledge'" - that he is liable for them on account of two tools, not that they are two [separate] commandments. And the language of the Sifrei (Sifrei Devarim 272:1) about this matter is - they said, "Just as a lower millstone and an upper millstone are distinct in being tools performing one task, for which one is liable for this one on its own and that one on its own; so [too for] all two tools performing one task is one liable for this one on its own and that one on its own." And the explanation of the statement is that even though they are used to do the same task, he is liable for this one on its own [and for that one on its own]. If one transgressed - took it as collateral and grabbed it from him - they remove it from his hand and return it to its owners. But if [it was lost] or burnt before he returned it, he is lashed; and likewise with the garment of a widow. And the regulations of this commandment have already been explained in the ninth [chapter] of [Bava] Metzia. (See Parashat Ki Teitzeh; Mishneh Torah, Creditor and Debtor 3.)