LAWS OF THE THREE WEEKS AND NINE DAYS
The "Three Weeks" between the 17th of Tammuz and the Tisha B'Av have historically been days of misfortune and calamity for the Jewish people. During this time, both the First and Second Temples were destroyed, amongst other terrible tragedies. These days are referred to as the period "within the straits" (bein hametzarim), in accordance with the verse: "all her oppressors have overtaken her within the straits" (Lamentations 1:3).
On Shabbat during the Three Weeks, the Haftorahs are taken from chapters in Isaiah and Jeremiah dealing with the Temple's destruction and the exile of the Jewish people.
During this time, various aspects of mourning are observed by the entire nation. We minimize joy and celebration. And, since the attribute of Divine judgement (“din”) is acutely felt, we avoid potentially dangerous or risky endeavors.
ASPECTS OF MOURNING DURING THE THREE WEEKS
1. No weddings are held. (However, engagement ceremonies are permitted.)
2. We do not listen to music.
3. We avoid all public celebrations -- especially those which involve dancing and musical accompaniment.
4. We avoid exciting and entertaining trips and activities. (Kaf HaChaim - OC 551:41)
5. No haircuts or shaving. (Fingernails may be clipped up until the week in which Tisha B'Av falls.)
6. We do not say the blessing She-hechianu on new food or clothes, except on Shabbat.
THE NINE DAYS
The period commencing with Rosh Chodesh Av is called the "Nine Days." During this time, a stricter level of mourning is observed, in accordance with the Talmudic dictum (Ta'anit 26): "When the month of Av begins, we reduce our joy."
(1) We avoid purchasing any items that bring great joy.
(2) We suspend home improvements or the planting of trees and flowers.
(3) We avoid litigation with non-Jews since fortune is inauspicious at this time.
(4) We abstain from the consumption of meat (including poultry) and wine. These foods are symbolic of the Temple service and are generally expressions of celebration and joy.
• On Shabbat, meat and wine are permitted. This applies also to any other seuduat mitzvah -- for example, at a Brit Milah or at the completion of a tractate of Talmud.
• Wine from Havdallah should be given to a child to drink.
(5) We refrain from wearing newly laundered garments or laundering any clothes.
• If the "freshness" has been taken out of a garment prior to the Nine Days, it may be worn.
• Fresh clothes may be worn for Shabbat.
• The clothing of small children, which gets soiled frequently, may be laundered during the Nine Days.
• Clothes may not be laundered even if done in preparation for after Tisha B'Av, or even if done by a non-Jew.
(6) We do not bathe for pleasure.
• It is permitted to bathe in order to remove dirt or perspiration, or for medical reasons. This may be done only in cool water.
• Furthermore, the body should be washed in parts, rather than all at one time.
• Bathing in warm water is permitted on Friday in honor of Shabbat.