The term “Tisha B’Av,” means “the ninth of av.” “Av” is the fifth month of the Jewish year, so “Tisha B’Av” refers to the ninth day of the month of Av.
Tisha B’Av is the day that both Holy Temples were destroyed. The First Holy Temple was destroyed in the year 3338 after Creation (422 B.C.E.). The Second Holy Temple was destroyed 490 years later, in 3828 after Creation (68 C.E.).
It was a day marked for evil. On that day in 2448 (1312 B.C.E. — 890 years before the Destruction of the First Temple), the Children of Israel accepted and believed the false report of the Spies (see Numbers 13:1-14:45.) On that day, Hashem decreed that because of this sin the generation that left Egypt would not enter the Land of Israel, and only their children would, forty years later. Moreover, Hashem decreed that later evils would befall the Jewish People on the anniversary of that day.
And, sadly, this has proven true. On that day, in 3893 (133 C.E.), the city of Beitar was destroyed during the Bar Kochba revolt. And on that day (I guess in 3894 after Creation — 134 C.E.), the wicked Tinneius Rufus, Roman Governor of Israel, plowed over the site of the Holy Temple. Many later events throughout our history also took place on Tisha B’Av, such as the expulsion of the Jews from Spain in 1492. World War I began, which, it is said, was the direct cause of World War II, a tragic time for world history, and particularly for the Jews.
For more events that took place on Tisha B’Av throughut the millennia, visit the Ohr Somayach website
The primary reason for the fasting and other observances of Tisha B’Av, however, is because on the Ninth of Av the enemy set fire to the Holy Temple.
Therefore, on this day we observe a greater level of mourning than during the rest of the Three Weeks. We mourn the destruction of Hashem’s Holy House, which was and will be our greatest location of blessing and spirituality; we mourn the Exile of Hashem’s Glory; we mourn the scattered exile of all Jews and the pain and suffering we have been through and are still put though in many places; we mourn the fact that we cannot keep all the Commandments because there is no Holy Temple; we mourn the fact that we cannot conduct our own lives entirely as Hashem wants us to because we are under the subjugation of other people.
Thus, on Tisha B’Av, from the night before until the stars come out at the end of the day (approximately 25 hours in most areas) we may not eat or drink anything at all—not even water. (We may not even wash out our mouths.)
Note that unlike any other fast besides Yom Kippur, the fast begins the night before. All fasts, except Yom Kippur and Tisha B’Av, begin in the morning and last until the night. Only Yom Kippur and Tisha B’Av span a night and a day, lasting about 25 hours each.
(The reason it lasts 25 hours and not 24 is because it is not clear if a new day begins (and the previous day ends), according to the Torah, when the sun goes down or when the stars come out. Therefore, to cover all the bases, we begin when the sun goes down and continue until the next day when the stars come out. This prevents us from transgressing the Law at either time.)
On Tisha B’Av you may (and must) feed your pets or other animals that depend solely on you for food.
We may not bathe. When we wash our hands at any time in the day—even when we first wake up in the morning— we wash only up to the joints at the base of our fingers and not the rest of the hand. We may wash areas that have become soiled or stained, but no more than that.
We may not wear footwear that has any leather (other leather clothing, such as a leather belt or leather gloves, is permitted). It is forbidden to have marital relations.
We sit on the floor or on cushions or very low chairs, and not on regular chairs or benches. (This last is in effect only from sunset the night before until half-day on Tisha B’Av. After that time, we may sit on regular chairs.)
Anything needed for medical reasons is permitted (and is sometimes compulsory, if the doctor says so).
Levity, games, or any activity that takes one’s mind off mourning (except sleeping) is forbidden. We may not greet each other. We may not give or accept gifts (charity is permitted). We should not conduct business. Going to work is permitted only if financial loss will be caused otherwise, or if you could lose your job. Housework should not be done. Preparing food is permitted after midday.
Before midday, smoking is prohibited. After midday, if you absolutely must smoke, you may smoke in private.
The study of Torah is also forbidden, except for things that are appropriate on Tisha B’Av. This is because the Torah says «Hashem’s Laws are righteous, they make the heart happy…» (Psalms 19:9).
However, it is permitted to study topics of Torah that are relevant to Tisha B’Av or to mourning. Some examples of these are the Book of Lamentations and its commentaries, the story of the Destruction of the Holy Temple as told in the Talmud and other Rabbinic Writings, the Laws of Tisha B’Av, the Book of Job and its cmmentaries, the Laws of mourning, and the warnings of the Prophets before the Destruction.
Tisha B’Av is not a Holiday. We may drive our cars, turn on and off lights, and so forth, like any other weekday.
Everything forbidden during the Three Weeks and the Nine Days is forbidden on Tisha B’Av. We may not listen to or play music, take haircuts (like in the Three Weeks); we may not go swimming or wash our clothes (like in the Nine Days).
On the night of Tisha B’Av we read the Book of Lamentations after the Nighttime Prayer, and recite a few «Kinnot,» special prayers for and about Tisha B’Av. We pray Shacharis (the Morning Prayer) without tallit and without tefillin, because they are adornments of pride and joy. After Shacharit we recite a lot of Kinnot.
We wear our tallit and tefillin for the afternoon Mincha prayers.
All this mourning is done to spur us to full repentance.
The month of Av is also called Menachem Av, the consoling month of Av. This is because we hope and pray that Hashem will soon turn this time of sadness into a time of joy by bringing us the Rescue From Exile that we have been awaiting for almost 2,000 years. Then we will be able to serve Hashem as He wants us to.
When that time comes, and the Holy Temple is rebuilt, when all the Jewish People will return to the land of Israel, when we will have no enemies, when all Jews will know Hashem, study Torah and understand and observe the Commandments, when all the world will accept Hashem as the Al-mighty, and everyone will live in peace, at that time Tisha B’Av will become a day of joy and a Yom Tov (Jewish Holiday).
May Hashem make this happen soon!