There are five categories of abstinence which must be observed on Tisha Be’av: Eating and drinking, washing one’s self, rubbing one’s body with oils or lotions, wearing leather shoes, and marital relations. Our Sages also prohibited learning Torah on Tisha Be’av, for the words of Torah gladden the heart. The only portions of Torah that one may delve into on Tisha Be’av are the book of Iyov (Job), the prophecies regarding the destruction of the Temple in the book of Yirmeya (Jeremiah), the portions of Midrash and Talmud regarding the destruction of the Temple, the laws of mourning, and the like. One may likewise learn Mussar works which arouse one to repent and humble the heart.
On Erev Tisha Be’av, one may only eat until several minutes before sunset. The five categories of abstinence we have mentioned above take affect beginning from sunset.
One may not wash one’s body on Tisha Be’av with either hot water or cold; this applies to one’s entire body or even just partially. One may not even stick one’s finger into water (for pleasure). Thus, on the morning of Tisha Be’av, one should wash his hands (“Netilat Yadayim”) only until one’s knuckles the way one washes the rest of the year, i.e. three times on each hand while alternating hands, and then recite the blessing of “Al Netilat Yadayim.” After using the restroom, one should wash his hands the same way, only until the knuckles.
One should not wash one’s face on the morning of Tisha Be’av; rather, after one washes his hands, before drying them while they are still wet, one may rub them over his eyes. If one has eye residue or any other filth in or around one’s eyes, one may wash the affected area. If one is extremely concerned about one’s personal hygiene and does not feel at ease with himself without washing his face in the morning, one may indeed do so on the morning of Tisha Be’av.
A new bride who is still within thirty days of her marriage may wash her face on the morning of Tisha Be’av so that she does not become repulsive to her husband.
Regarding the fast of the Seventeenth of Tammuz (and other such public fasts), if it is extremely difficult for one to abstain from brushing one’s teeth on the morning of the fast, one may act leniently and brush his teeth while taking care not to swallow even a drop of water. Additionally, one must take care not to put a “Revi’it” (81 ml, approximately 2.7 oz.) of water into one’s mouth at once. Nevertheless, on Tisha Be’av one should not act leniently unless one will suffer immensely without doing so or if one suffers from bad breath, in which case, one may indeed act leniently on the condition that one tilts his mouth downwards in order that the water not reach his throat (in addition to the aforementioned conditions). One should not rely on this leniency on Yom Kippur though.