Shalom dear Rabbi, I know that this is a basic question, but I never really found an answer to it. I know that it is forbidden to 1.carry money on Shabbat (even if there is an eruv), 2. to buy things on Shabbat but from what I understood it is permitted to carry a voucher on Shabbat for a meal (eg. a meal at a Jewish event) My questions are 1.what is the actual source that it?s forbidden to carry money on Shabbat? (is it muktze because it is used for buying things and/or it is part of week-day activities ?) I would be thankful if you could point to a source where I could deepen my understanding of the halachic reasons (I know that it?s forbidden but so far I?m only guessing what the reason is) 2. why it is forbidden to buy things (is the reason that it is weekday activity for both the seller and the buyer, even if none of the 39 Melachot are perfomed?) I would also be thinking about a situation with a chewing-gum vending machine (within an eruv) that is completely mechanical and operates with a coin and a lever that is being turned by the buyer and where the sale does not (seem) to involve any of the 39 Melachot. And what is the reasoning for the voucher being allowed? Is the reason that the voucher is only PROOF of an earlier payment (the payment having been made before Shabbat) and the assumption is that (especially at a Jewish event) no extra Melachot would be performed, i.e. the person with the voucher would be served his food and the people who serve the food are assumed not to do Melachot in the process?) Thank you very much!!

Shalom, Thank you for your question. You touch on many issues that obviously need extensive learning and research – but in the short space available to us in this internet format, let me try and give some broad outlines of the topics involved. There are two issues involved in using money on Shabbat. The first is that it is forbidden to transact commerce (buying and selling) on Shabbat. Even though this is based on a verse Isiah 58 (13-14), there are many sources that explain that commerce is in fact forbidden from the Torah (and not just the early Prophets) – see for example the Ramban on Leviticus 23,24, and the response of the Chatam Sofer (Choshen Mishpat 195). They explain that the Torah commands us a "day of rest" which includes the resting from commerce. Whatever the source – buying and selling are forbidden on Shabbat according to all opinions. (This includes not only the use of money, but also other forms of commerce – for more detailed explanations of this law, see the work Shmirat Shabbat KeHilchatoh, chapter 29). Once commerce is forbidden, the money itself was classified as "mukzah", that is objects that are forbidden to move on Shabbat. This is a Rabbinic enactment. One of the reasons for it is to create a fence around forbidden activities. So, being that buying things is forbidden, the Rabbis forbade even the movement of money. Your question about the use of a pre-paid voucher (for a Shabbat meal etc), is also addressed in the work Shmirat Shabbat KeHilchatoh (Chapter 29, 25), and the permission is based, as you wrote, on the fact the voucher is only proof that the meal was paid for – and not itself currency. The question about a vending machine can also be found there (29, 27-28). The use of such machines is forbidden because it is a form of commerce, which, as we explained is forbidden on Shabbat. I hope this brief outline is of some help to you. Blessings.