Washing one’s skin is forbidden on Tisha B’Av, including even putting one’s finger in water without justification.[2] When there is justification, such as for the need of a mitzva, it is permissible to wash as much as is necessary.[3] There are other justifications besides mitzvot. The gemara[4] says that one whose hands are dirty may wash his hands normally on Yom Kippur (and therefore certainly on the less stringent Tisha B’Av). In explaining this halacha, the Tur[5] says that only washing for enjoyment is forbidden.
Accordingly, there is logic to say that since few people intend to get washing enjoyment from doing dishes, it should be permitted to wash dishes normally on Tisha B’Av. However, there are strong indications that we permit non-enjoyment washing only under specific circumstances that justify it. For example, the gemara[6] allows one to wade through water on Yom Kippur on the way to visit his rabbi (a mitzva), but leaves open the question of whether the rabbi may go to visit his student.[7] One can claim that wading through water is more likely to be an enjoyable form of real bathing, which thus requires a more serious justification. Similarly, when one is allowed to wash his hands for a mitzva need, he must wash only the minimum area of the hand that is necessary, not the whole hand, as we normally prefer.[8] This does not seem to be a particularly significant form of enjoyment, and thus our concern for how it is done seems to indicate that there must be a clear necessity even when one does not intend to wash for enjoyment.
We do find that preparing a meal is a legitimate justification to get one’s hand wet. The gemara[9] allowed doing “keniva” of vegetables toward the end of Yom Kippur, so that one will have peace of mind that he will be ready to eat when the fast ends. The Rashba and Ramban[10] explain that keniva is washing, and we thus see that the fact that one’s hands will undoubtedly get wet in the process does not prohibit it. (We do not practice this leniency, but for an unrelated side reason.[11])
The Magen Avraham[12] further says that women who are cooking on Tisha B’Av may wash meat even though their hands will get wet. This ruling, however, is far from straightforward. The Pri Megadim[13] makes two comments on this opinion of the Magen Avraham. One is that it is referring to someone who needs meat. The Machazeh Eliayhu[14] understands that the Pri Megadim was bothered by the fact that it is forbidden to eat meat until the next afternoon (the 10th of Av). He infers from the fact that the Pri Megadim felt it necessary to point out that the person needs the meat earlier that it would be forbidden to wash one’s hands while cooking on Tisha B’Av for the next day’s meal. The Pri Megadim’s second comment is that one should not use warm water, which is a higher level of enjoyment. The Kaf HaChayim[15] takes issue with this, at least in cases in which warm water is necessary for the cooking, and it seems logical to be lenient in that case.
The matter of avoiding touching water when possible is the subject of another disagreement. The Beit Yosef[16] and Taz[17] maintain that when a child must be washed on Yom Kippur, a non-Jew should do it, so that the Jew can avoid the pleasure of touching the water. However, the Magen Avraham[18] and most authorities rule that when it is permitted for the child to be washed, a Jew may wash him.
In the final analysis, it is permitted to wash only those dishes that are needed to be washed on Tisha B’Av. Some examples are: to avoid flies and odors, to make sure that as many dishes as are required will be available for those who must eat on Tisha B’Av, or to break the fast right afterward. In other cases, one should either use rubber gloves or wait until after Tisha B’Av. Irrespective of issues of washing, housekeeping type activities that can be delayed should be done only after chatzot.[19]