SEIF 7 (CONTINUED)
A BED THAT WAS DESIGNATED TO HOLD MONEY- PART THREE
The Tosfos Shabbos brings the Rashba's Shita that a utensil that doesn't perform a Malacha, but a Malacha is done on it (like a pot which doesn't cook the food per se, but rather you cook in it) is not a Kli Shemalachto L'Issur (a utensil which main use is forbidden.) He wants to say this is the reason why the Rif considers the bed permitted to move, since the bed doesn't do any Issur, rather the money is placed on top of it. He wants to say that the Rosh also agrees to this, since he only disagrees on the premise that it's a Chesaron Kis, but if it wouldn't be, he would agree that it's a Kli Shemalachto L'Heter.
The P'nai Yehoshua asks: How can a Kli Shemalachto L'Heter, become prohibited because of Chesaron Kis? (If we say that it's completely Heter on Shabbos, just because you won't use it for any other use, how can that make it completely Muktza if it's completely Heter.)
The Tosfos Shabbos wants to answer, that the reason the Rashba holds it's Heter and not Issur, since the whole concept of a utensil should be Muktza is a novelty (since we hold like R' Shimon that is lenient by Muktza) and we shouldn't stretch it to include utensils that Malacha is done on them, only if it actually does a Malacha. But in combination that it's also a Chesaron Kis, we need to be more stringent and prohibit it. At least it should get a little more of a stringent status and graduate to being a Kli Shemalachto L'Issur. This could be the reason of the Bais Yosef and Rama that say that the bed has a status of Kli Shemalachto L'Issur even though it has the characteristic of Chesaron Kis.