For the next three weeks, observant Jews will not marry, listen to music, buy or wear new clothing, take a pleasure trip, cut their hair or shave.

During the last nine days of the period, they also will refrain from consuming meat, fowl or wine (except on the Sabbath), sending gifts, doing laundry, bathing for pleasure and swimming.

And on the final day of the three weeks, they will not eat, drink, bathe, wear leather shoes or engage in sexual relations. Instead, they will spend that evening sitting on a low chair or on the floor of their dimly lighted synagogues as the Book of Lamentations is mournfully chanted. The next morning, again on the floor, congregants will read mournful Hebrew poetry.

Not exactly great summer fun. But these mourning rituals are part of the observance surrounding Tisha B'Av, the saddest day of the Jewish calendar. Tisha B'Av, which means the ninth day of the Hebrew month Av, runs from sundown July 17 through July 18.

Tisha B'Av commemorates the destruction of the first and second temples in Jerusalem and other tragedies in Jewish history - from the Crusades and Spanish Inquisition to the Holocaust. It also marks the culmination of a three-week mourning period that began yesterday with the fast of the 17th day of the Hebrew month of Tamuz - when Jerusalem's walls were breached - and intensifies in the last nine days.

"Tisha B'Av is a national day of remembrance for all Jewish people who suffered and died just because of their adherence to the Jewish faith," said Rabbi Hillel Baron of the Lubavitch Center for Jewish Education in Columbia.

The first temple was destroyed by Babylonia in 586 B.C. after it had stood for 410 years. The second temple, rebuilt 70 years later, was destroyed by Rome in 70 A.D. Roman armies leveled the Temple Mount, leaving the outer wall on the courtyard's western side that today is known as the Western Wall.

"Jews are always focused on hope, on joy," said Rabbi Susan Grossman of Columbia's Beth Shalom Synagogue. "But one day a year, we cry for the things that haven't happened and weep for all the destruction and all the death. There is a time for joy and a time for sadness. For us to be complete, we have to focus on sadness at least one day a year."

But according to 12th-century Jewish philosopher Moses Maimonides, Tisha B'Av will be transformed into a festival when the messiah arrives. "Hopefully, by correcting our past mistakes, we can pray for the fulfillment of the biblical prophecies for the ingathering of the exiles and rebuilding of the temple," Baron said.

Following the teachings of the late Lubavitch leader Rabbi Menachem Mendel Schneerson, Baron will encourage congregants to perform "extra" acts of kindness and charity during the three weeks and study how the temple would be rebuilt.

As part of an interfaith study program, Grossman spoke this week about Tisha B'Av and Jerusalem's significance to Jews at Locust United Methodist Church Summer Bible Camp. The program continues July 16 and 17.

During Tisha B'Av at Beth Shalom, where a black cloth will drape the ark housing the Torah scrolls, Grossman will bring in readings of Jerusalem falling and other tragedies, and will speak about the Middle East crisis.

"When Jerusalem reunified in 1967 [during the Six-Day War], the question was raised, 'Do we still observe Tisha B'Av?' The answer was 'Yes' because Tisha B'Av provides one day a year when we mourn deeply in our souls for all the pain that still exists," Grossman said. "And Israel is not at peace. Tisha B'Av commemorates that Israel is not at peace and secure, or reached its full potential as a Jewish state."

Rabbis said their congregants observe the three weeks to varying degrees - despite the lures of summer. "It's a challenge," Baron said. "But we forgo certain personal pleasures to allow us to think more in spiritual terms."

Even at wedding ceremonies, the groom breaks a wine glass to recall the temples' destruction.

For Alan Zeman, a Beth Shalom congregant, the three weeks is a link to the past. "There are times in the Jewish calendar when you have to remember," said Zeman, a Silver Spring physical therapist. "You remember your past, your heritage, where you came from."

But even in despair, Jews can be optimistic, said Nechie King, a Lubavitch congregant and Towson University professor. "Within that very sad time is the promise of redemption. So in thinking what we lost, what we can gain is the future."