- Peninei Halakha
The Three Weeks, which begin on the night of Shiv’a Asar Be-Tamuz and continue through Tisha Be-Av, are a painful time. This period is often known as Bein Ha-metzarim, recalling the verse, “All her pursuers overtook her in the narrow places (bein ha-metzarim)” (Eikha 1:3). Therefore, the Sages recommended that we take extra precautions on these days, which are prone to calamity. For example, even though one must always be careful and vigilant, those who go on a hike or swim in the sea must be even more careful during this period (see Eikha Rabba 1:29).
In order to signify the nature of this period, the Sages instituted the reading of special haftarot that deal with calamity on the three Shabbatot of the Three Weeks. On the seven Shabbatot following Tisha Be-Av, we read seven haftarot of consolation (sa 428:8, based on Pesikta).
Even though the Sages did not make any special enactments to mark the suffering and mourning of the Three Weeks, the Jewish people adopted the custom to refrain from music and dancing, and to avoid reciting She-heĥeyanu during this period.
There are other customs of mourning that various communities have adopted. Ashkenazim and some Sephardim, including Jews from Morocco and Djerba, refrain from cutting their hair during the Three Weeks. Other Sephardim are strict about this only during the week of Tisha Be-Av. Ashkenazim, Yemenites, and most Sephardim do not conduct weddings during the Three Weeks. Other Sephardim are more lenient, only avoiding weddings from the beginning of the month of Av (see below, section 7).
In the following sections we will discuss at length the customs of the Three Weeks, the Nine Days, and the week of Tisha Be-Av.
 Even though Shiv’a Asar Be-Tamuz begins at daybreak, the customs of mourning of the Three Weeks begin the night before. As we learned above, the fast was originally supposed to begin at night. The reason we begin fasting in the morning is that there are no harsh decrees against the Jewish people today. Therefore, it is up to the Jewish people to decide whether or not they want to fast, and they have decided to fast only from daybreak. However, the Three Weeks begin on the night of 17 Tamuz. Ĥida writes in this vein in Responsa Ĥayim Sha’al 1:24, based on Ramban. R. Moshe Feinstein, in Igrot Moshe oĥ 1:168, however, rules leniently, permitting weddings on the night of 17 Tamuz. Elsewhere (oĥ 4:112:2), he allows one to cut one’s hair then, if there is a great need. Tzitz Eliezer 10:26 disagrees, forbidding even weddings – through which one fulfills a mitzva – on the night of the seventeenth, because the Three Weeks have already begun. This seems correct.