One doesn’t have to be superstitious to recognize facts. It is a historical fact that the period between the seventeenth of Tammuz and the tenth of Av was plagued by recurring tragedies. The door to our troubles first opened on that seventeenth day of Tammuz when Moses walked in on the worshippers of the golden calf and shattered the tablets of the law.
On the same date, in the eras of the First Temple and the Second Temple, the daily sacrifice, known as the tamid, which expunged the sins of the Jews and granted them divine amnesty, was brought to a halt. On the seventeenth of Tammuz the walls of the Second Temple were breached by the enemy, who ultimately razed the Temple to the ground on Tisha B’Av.
Also on the same date, Apustomus (circa 150 BCE), one of the Syrian leaders with whom the Hellenists collaborated in the persecution of religious Jews in Israel, publicly torched a Sefer Torah. And on the seventeenth of Tammuz, Menasheh, king of Judah, erected an idol in the Temple. For these reasons this period is called “Between the Straits” (Bein Hametzarim), based on the verse in Lamentations “all [Israel’s] persecutors overtook her between the straits.”
Thus, based on the laws of personal mourning, the Three Weeks, from the seventeenth of Tammuz to the tenth of Av, are observed as a period of national mourning. In the case of a personal tragedy, such as the death of a relative, the mourning commences after the event, with the observance of the most severe restrictions of the shiva, followed by the less severe restrictions of the Sheloshim, followed by the least severe restrictions of the eleven months. In the case of Tisha B’Av, the reverse is true. The mourning commences beforethe event, with the observance of the least severe restrictions (akin to the eleven months) during the first period between the seventeenth of Tammuz and Rosh Chodesh Av. Stricter restrictions of mourning follow during the second period between Rosh Chodesh Av and Tisha B’Av. The strictest restrictions of mourning are observed on Tisha B’Av itself.
Accordingly, commencing with the first period, between the seventeenth of Tammuz and Rosh Chodesh Av, the following are some of the activities to be avoided: weddings, playing musical instruments for pleasure, and reciting the Shehecheyanu blessing in connection with wearing new garments or tasting new fruit. Some practice the custom of refraining from shaving or cutting hair even during the first period.
The following activities may be indulged in during the first period: engagements, with or without a festive meal, until Rosh Chodesh Av; a pidyon haben (ceremony of redemption of a first born), even after Rosh Chodesh Av; and attending a brit with a festive (milk or meat) meal up to noon on Erev Tisha B’Av. According to Rav Moshe Feinstein, the first period commences on the morning of the Seventeenth of Tammuz rather than the night following the sixteenth of Tammuz. Accordingly, Rav Feinstein permits in extenuating circumstances weddings and haircuts on the evening preceding the fast of Shivah Assar B’Tammuz.
Commencing with the second period, between Rosh Chodesh Av and Tisha B’Av, the following are some of the additional activities to be avoided: consumption of meat and poultry, drinking wine, laundering or wearing freshly laundered clothing, swimming, painting or other forms of home decorating, planting flowers and plants, as well as any risky activity (such as lawsuits, scheduled surgery, and travel, to the extent it can be postponed without adverse effect).
On Shabbat during the Nine Days one may don freshly laundered clothes, eat meat and drink wine, including Havdalah. Similarly, the usual Shabbat songs should be sung both in the synagogue and at home. A commonly employed and permissible device regarding the prohibition of wearing fresh clothes during the Nine Days is to don them for a moment or two before the Nine Days.