The Shulchan Aruch (Orach Chaim 251:1) rules: “If one does work on erev Shabbos from Mincha time and on, he won’t see any blessing.” The Mishnah Berurah (s.k. 2) explains: “From that particular activity - even if he gains now, he will lose out somewhere else”.
However, in Hilchos Purim (696:1) the Shulchan Aruch writes: “On Purim one is allowed to work. In a place where the custom is not to, one shouldn’t, and one who does won’t see any blessing from that work, forever.” The Mishnah Berurah (s.k. 3) writes: “For example, if one plants something, it won’t grow (Beis Yosef). However, the Re’am writes: He won’t gain, however, he won’t lose either (Magen Avraham)”.
Not Seeing Berachah, Even from Work Done After Chatzos [Midday]
The Shulchan Aruch (554) has two seifim regarding the issur to work on Tisha B’Av. In sif 22 it says: “In a place where the custom is to work on Tisha B’Av, one may. In a place where the custom is not to, one shouldn’t. In all places talmiday chachomim don’t work, and anyone who wants to act like a talmid chocham (i.e. not work) is allowed to”.
Then in sif 24, the Mechaber says: “Anyone who works on Tisha B’Av, won’t see any berachah from that work.” The Magen Avraham (s.k. 27) points out, that from the second halachah it seems that even if one is in a place where the minhag is to work, one still won’t see any berachah from his work. In sif 22 the Shulchan Aruch differentiates between a place which has the custom to work and a place which doesn’t, however, in sif 24 he doesn’t, therefore, it seems that it applies in all places. The Magen Avraham makes the same diyuk from the Rif, Rosh and Tur.
From the conclusion of the Magen Avraham it’s clear, that even if one does melachah after chatzos and takes his mind off aveilus [mourning], he also won’t see any berachah. Although the Rema (sif 22) rules that the issur to work on Tisha B’Av only applies until chatzos, the Magen Avraham still learns that one won’t see any berachah from such work. The Magen Avraham then wonders why people aren’t careful about this? And he suggests its because it’s clear from the Gemara that it’s only a problem if one sets himself up for work (קובע עצמו למלאכה) and takes his mind off aveilus, if one works, however, but not fixed and doesn’t take his mind off aveilus, then he may still see berachah from his work.
Based on all the above information, we must try and determine if running day camps on Tisha B’Av to help the mothers fast is a problem or not. Certainly, in the morning when we follow the minhag that there is an issur to work there is what to be discussed, but even in the afternoon where the minhag is that one may work, there is still an issur for one to take his/her mind off aveilus, and no berachah will be seen from the money (according to the Magen Avraham). According to the Machatzis HaShekel, not only will no berachah be seen from the money earned on Tisha B’Av, but if the girls decide to make a day camp/play group at some other time during the year, they won’t see any berachah then either, and they will be suffering a loss year round.
