It says in Choshen Mishpat Siman 195 sif 11 that a kinyan suddor may not be made on Shabbos. If someone was over and did make such a kinyan then the kinyan is good.
As well in Choshen Mishpat Siman 235 sif 28 if someone is mocher or koneh kinyan b’Shabbbos af al pi sh’macin oso on that which he was over dvrei chochamim still the maseh is kayum.
In Hilchos Shabbos Orach Chaim Siman 306 sif 4 it says that scar Shabbos is ossur. The M”B brings that the reason is a gezera because of mecach u’memcar (Rashi in Kasubos daf 64).
My question is like this, why is it when it comes to scar Shabbos we say it’s ossur a gezera because of mecach u’memcar. And when it comes to actual mecach u’memcar we say the kinyan is good and don’t make any kanas or gezeras over there. What’s the difference? Why is the gezera more chomer than the actual maseh of mecach u’memcar itself.
Thanks for your time and insights.
Answer:
The difference is possibly that in the case of sechar Shabbos the contract between the worker and the employer is flawed. This is similar to a contract for payment of ribbis (forbidden interest). Because the contract is flawed, it is null, and there is no obligation to pay the ribbis. Here, too, the flaw in the contract leads to the result that there is no obligation to pay the wages.
In contradiscinction, the case of making a transaction on Shabbos involves no contractual flaw. In fact, the contract is fine, and the flaw lies only in the fact that the contract was implemented on Shabbos by means of the kinyan. Therefore, the contract is not voided, and in spite of the transgressoin, the goods in question transfer from the buyer to the seller.
After the goods transfer to the buyer, the buyer is obligated to pay for them, and this does not involve sechar Shabbos.
Note that there is a dispute among authorities as to whether the money a person receives as sechar Shabbos is prohibited to him or not (see Biur Halachah 245, s.v. Assur). The question is whether the prohibition was extended (like ribbis) beyond the actual earning of the money, or not. In the case of the Shabbos transaction, where there is no contractual problem and therefore no case of sechar Shabbos, there is no case for ‘extending’ the effect.
Please see https://dinonline.org/2011/08/22/betting-on-shabbos-horseraces/, where we gave a slightly different definition.
