בבא בתרא פה.
"כליו של לוקח ברשות מוכר"
Rav and Shmuel say that כליו של לוקח are קונה for him in any place, except if the כלי is in רה"ר. The רשב"ם explains, when an item is placed in the כלי of the לוקח, it is viewed as if it was placed in his חצר. [פה:] ר' ששת asks: if the price was already agreed upon and the seller placed the item in the כלי of the לוקח, which is in the רשות of the מוכר, does the purchaser’s כלי acquire for him or not? Do we say the רשות they are standing in is the עיקר and since it’s the רשות המוכר, the כלי של לוקח is בטל to the רשות and cannot be קונה, or once it’s in the כלי, it’s considered in the חצר of the לוקח? The [ה, טו'] רא"ש says that since our Gemara does not come to a resolution, we pasken that if the כליו של לוקח are in the רשות of the seller, it is not קונה.The שו"ע [חו"מ ס' ר',ג'] paskens, any place a person has permission to place his כלי, it will be קונה for him and once the item is placed inside, neither the seller nor purchaser may back out. Therefore, one’s כלי cannot be קונה for him in a רה"ר since he doesn’t have permission to put his כלי there. Nor are his כלים קונה for him in the רשות המוכר unless the מוכר says be קונה with this כלי.
The שו"ע [יו"ד רנט] says that if one says, "סלע זו לצדקה" or "הרי עלי סלע לצדקה", even if he separates it, as long as the money has not reached the hands of the גבאי yet, he may borrow it or lend it to someone else and replace it with other money. Once it is "בא ליד הגבאי", it is אסור to borrow it or lend to other people. Poskim discuss what status does money in a pushka have? It would seem to depend on our Gemara. If we say that when given permission by the מוכר, even if in the רשות המוכר, we still say כליו של לוקח קונה, then it would seem that once the money is placed in a pushka, it should be considered as the עניים were קונה it and it’s בא לידי הגזבר, since the בעל הבית gave them permission to place it there. Consequently, it should beאסור to use. ר' חיים קניבסקי [דרך אמונה, מתנות עניים פ"ח אות קכא'] brings a י"א that a קופת צדקה that hangs in people’s homes, once the money is placed inside them, it’s considered בא ליד הגבאי and it’s אסור to exchange or lend. In ציון ההלכה he says, עיין מאמר מרדכי. There he paskens [ס' טו] that once money was placed in a pushka, one may not take out the money and give it to a different tzedakah, because it is considered בא ליד הגזבר of this specific tzedakah organization. He also discusses, since הקדש can’t be קונה with חצר, why should the pushka be קונה, it’s using קנין חצר? ע"ש.ר' חיים therefore suggests, that when one hangs up a pushka he should make a תנאי that it should not be קונה the money he puts in. This way, he will be able to use it, as he is not giving permission for the לוקח to be קונה. [משנה הלכות ס' קנז] ר' מנשה קליין discusses this topic and relates that as a young boy he would see his mother borrow from the pushka in the house and when she replaced it, would add extra. He says this מנהג might be based on the שו"ע that says if the עניים have הנאה, then the גבאי may utilize the money. ר' חיים above explains [אות כח] that this also allows the גבאי to swap small bills for larger ones, as this makes it easier to guard and transport the cash, which is a benefit to the עניים.