647. "Shouldn't Talk About It on Shabbos"

90:4 Isaiah 58:13 also tells us that we honor Shabbos by not speaking of mundane things; the Sages understood this to mean that our speech on Shabbos should not be like our speech during the week. Therefore, we may not say things like, "I will do such-and-such thing tomorrow," or "I am going to buy this merchandise tomorrow." (There is a difference of opinion as to whether one may discuss on Shabbos the matter of a mitzvah to be performed after Shabbos. The Mishnah Brurah advises that one not do so unless it is actually necessary – MB 307:1.) This restriction only applies if the activity in question could not be accomplished in any way at all on Shabbos. An activity that could be performed in some fashion on Shabbos, even though it can't be done that way at this particular moment, may be discussed. Therefore one may say, "I am going to such-and-such place tomorrow," though he should not use language that suggests traveling by vehicle. One should not talk too much about such things; even too much idle chatter is prohibited on Shabbos. One may likewise not discuss things that cause distress on Shabbos. A person may not verbally calculate accounts on Shabbos, whether it's an upcoming account or a past account about which he still needs to know. For example, one may not say, "I spent so much for workers' wages on this building, leaving me with so much." One may calculate accounts that he doesn't need at all provided that he doesn't spend too much time on them, since excessive idle chatter is forbidden on Shabbos. (If another person needs this information, one may not calculate it on his behalf – MB 307:26.)

90:5 The Sages understood from the phrase "your affairs" that only one's personal affairs are forbidden, but G-d's affairs (i.e., matters of Torah and mitzvos) are permitted. Therefore, one can wait by the edge of the Shabbos boundary for Shabbos to end in order to travel to perform a mitzvah. Similarly, one may oversee community business on Shabbos, such as to go to government officials to speak on the community's behalf because handling the community's needs is like performing mitzvos. Similarly, one may talk to a teacher about taking his child on as a student to teach him Torah or even a trade. This is because learning a trade is also considered a mitzvah since if a person doesn't have an occupation, he will end up stealing to live. One may not, however, actually hire the teacher on Shabbos because hiring is completely forbidden on Shabbos, even for the sake of a mitzvah. Only activities that are prohibited based on Isaiah 58:13 are permitted for the sake of a mitzvah. One may announce finding a lost object on Shabbos because returning a lost item is a mitzvah. (This is true even if the lost item is muktzeh that the finder cannot return on Shabbos – MB 306:49.)