One may speak about activities that are prohibited on Shabbat if it is for the sake of a mitzva. In such a case, one may also examine sites where melakha must be done or make financial calculations for the sake of a mitzva. It is written: “and if you honor it, and not go in your own way, nor look to your affairs, nor speak of them” (Yeshayahu 58:13), and the Sages expound: “‘Nor look to your affairs’ – it is forbidden to look after your own affairs on Shabbat, but one may look after the affairs of heaven (‘ĥeftzei shamayim,’ i.e., religious matters)” (Shabbat 113a). Therefore, if necessary, one may walk to inspect a synagogue construction site. If something is needed for an upcoming wedding or funeral, one may walk to the edge of the teĥum so that one can deal with these matters immediately after Shabbat. Near the end of Shabbat, one may also start walking to a location from which people will be picked up after Shabbat in order to comfort mourners (Shabbat 151a; SA 306:3; SSK 29:13).
Similarly, in cases of necessity, one may speak about mundane matters that relate to mitzva needs. This includes calculating the costs of a wedding meal or a brit mila, as each of these is a se’udat mitzva (a festive meal associated with a mitzva). One may plan the hiring of a band for a wedding or deal with the bride’s dress. However, one may not actually close a deal, because business deals are prohibited even for the sake of a mitzva. It is altogether prohibited to discuss hiring a photographer for a wedding, or the purchase of wedding outfits for family members of the bride and groom, since these do not qualify as mitzva needs.
One may take up a collection in which everybody pledges to give a certain amount of money to charity or to a synagogue. Parents may calculate the sum needed for their children’s education, whether religious, secular, or vocational. Those involved in education may discuss school or class budgets. A principal may offer a job to a teacher and mention a salary figure, though it is forbidden to reach an agreement on wages. One may discuss communal needs such as paving roads or levying taxes, as the needs of the community are deemed mitzva needs (Shabbat 150a; SA 306:6). In all these cases, it is proper to be lenient only when there is a specific need. If the matter will be addressed in any case, it is proper not to speak of mundane matters or walk in order to inspect them, even for the sake of a mitzva (MB 307:1).
If necessary, one may announce that an object has been found on Shabbat, even if the item in question is muktzeh (such as a purse), in order to facilitate the fulfillment (after Shabbat) of the mitzva of returning a lost item (SA 306:12). In an area where it is difficult to locate matza for Pesaĥ or a lulav and etrog for Sukkot, one may announce on Shabbat where they are available for sale (MB 306:55).