Five catastrophic events that affected all Israel occurred on Tisha (the 9th) of Av.
On the 17th of Tamuz, Moshe Rabbeynu descended from Mt. Sinai after receiving the Tablets of the Commandments. On that day, the people were worshipping the Golden Calf. Moshe shattered the Tablets. The ones that replaced them were not the same as the first. The first Tablets contained a higher form of the Ten Commandments than those revealed on the second Tablets. With the giving of the Torah, we were supposed to have entered the messianic age. Moshe was supposed to have been Mashiah. Yet, we lost this marvelous opportunity. We were thwarted as we were centuries earlier in the Garden of Eden.

Years later, other horrible events occurred exactly on this day. Prior to the destruction of the holy Temple by the Babylonian ancestors of today's Iraq, the continual offering, which maintained the balance between Heaven and Earth, ceased on this day. On this day, years later, during the period of the Greek occupation, a pagan authority destroyed the oldest and most authoritative scroll of the Torah. On this day, that same Greek pagan then proceeded to place a pagan image in the holy Temple. On this day, years later, in their conquest of Israel and the genocide of her people, the walls of Jerusalem were breached. The 17th of Tamuz therefore, has become a day of fasting. From sunrise to sunset, every adult Jew (except nursing mothers and the ill) is to fast, neither eating nor drinking to commemorate all that we have lost on this day.

Three weeks later, on the 9th of Av, even greater catastrophic events occurred. When Moshe Rabbeynu sent out spies to the Promised Land, they came back and brought a bad report, filling the hearts of the people with fear. The entire nation mourned their fate and wanted to return to Egypt. This happened on Tisha B'Av. Years later, both the First and Second Temples were destroyed on this day. Years later, the Roman occupiers destroyed the final Jewish stronghold against them and murdered the entire population of the city, which numbered close to a hundred thousand innocent men, women, and children. This horror happened on Tisha B'Av. One year later, to the day, the Roman Nazi emperor decreed that a pagan temple be established on the holy Temple Mount. Tisha B'Av therefore is the day of days of national mourning for the entire Jewish people. All fast for a full 24-hours on this day. Also forbidden are bathing, adorning, marital intimacy, the wearing of leather shoes and the study of Torah.

There are numerous laws regarding the proper preparations and observances of the Tisha B'Av fast. One should consult with one's local Orthodox Rabbi for full and proper instruction regarding these laws in accordance to one's communal origins.
The history of this time speaks for itself about the tragedies that occurred therein. Yet, we must ask why did so many bad things happen all during the same time of the year and exactly on the same dates? As intelligent adults, we recognize that there is far more than a coincidence here. In order to understand the "why" of the Three Weeks, we must delve into the mysticism of the Torah. The secrets of time are revealed within Torah mysticism. They will provide for us the necessary insights to understand why all these terrible things happened and continue to happen in Tamuz and Av.

As is known each month of the year is dominated by an astrological influence. This was ordained by G-d. Insights into astrology help us to understand the mechanics of the universe. Yet, G-d created more than mere astrological influences. Over each month of the year and over each day of the month there is also the influence of the sefirot.

Yet, with Tamuz and Av, instead of joy we have sorrow. The reason for this is because just as the sefirot, elements and stars influence time, so more so does human behavior influence it. All things in creation have two sides to them, a side of good, and a side of evil. This is based on the verses in Kohelet made famous by the sixty's rock and roll song 'Turn, Turn Turn." There is a time to be born and a time to…

These three weeks are not a time for us to be mourning over the episodes of the past. Practically speaking, we have enough to mourn over our present. We cannot change the past. We cannot undo what has already been done. We can, however, change the future before it happens. We do this by changing our present.

Mourning the past is well and good. However, mourning the present is what is necessary. Changing the present is more than necessary, it is essential. Unless we change our course of action as individual Jews, as a collective nation, renew our covenant with G-d, and obey His commandments, we will inevitably come to experience new tragedies to mourn during these days. These three weeks emanate G-d's judgment upon the Jewish people, therefore, be careful during them. During these three weeks, Murphy's law is here most applicable - if anything can go wrong, it will, and at the worst possible time.

Click here for Sephardic Halachot of 3 Weeks

The following were excerpts of  'Beyn-HaMitzarim' by Rabbi Ariel Bar Tzadok, for more go to www.KosherTorah.com