The three weeks is an annual period of mourning of the destruction of the first and second Beit Hamikdash, the greatest tragedy in Jewish history, and the resultant Galut in which we still find ourselves in. It also mourns the other devastating events that occurred on the fast of Tisha B’av that falls at the end of the three weeks.
The three-week period, which begins with the fast of Tammuz and ends on Tisha B’av, is observed as a time of sadness and grieving. The three weeks have historically been ones of misfortune and calamity for the Jewish people, so joy and celebration are minimised, and risky and potentially dangerous endeavours are avoided.
On 17th Tammuz, the beginning of the three weeks, a multitude of misfortunes and tragedies befell the Jewish people, and many great catastrophes occurred during this time. Moshe broke the original 10 commandment tablets after seeing the Jewish nation worshipping the Golden Calf, the Jews were forbidden to make daily offerings by the Romans in 69 C.E. and Jerusalem’s walls were breached leading to the destruction of the second Beit Hamikdash three weeks later on Tisha B’av. And prior to the destruction of the Beit Hamikdash, idolatrous images were placed inside it and a Torah scroll was burnt by a Roman general.
During this time various practices of mourning are observed to lament over past tragedies. Similar to the period of the omer, no weddings or public celebrations are held, and exciting or entertaining trips are not taken. Haircuts or shaving are forbidden, music is not listened to and the Bracha she-hechiyanu is not made on new clothes or food, except on Shabbat.
The three weeks precedes the stricter level of mourning that is observed in the 9 days leading up to Tisha B’av when the intensity of the mourning reaches a peak. Meat and wine are abstained from, laundry is not washed and we do not bathe for pleasure during the 9 days. The fast of Tisha B’av, at the end of this mourning period, is a day that is spent entirely in mourning by fasting, praying and sitting on low stools or chairs.
All the laws of mourning are suspended on Shabbat, and if the fast falls on this day they are postponed until Sunday so that Shabbat can be joyously celebrated. Some say on these Shabbats our joy should be increased by adding extra dishes to show that we are not, in fact, in a state of mourning, but one of joyfulness.
The reason for the suspension of the mourning on Shabbat is that although the period of the three weeks and Tisha B’av has traditionally been those of exile, destruction, persecution and spiritual and physical estrangement, it is believed that this is ultimately for the best. Therefore it is encouraged that Shabbat should be celebrated as much as possible and should be a day of celebration and joy rather than one of mourning.