852. The Three Weeks

121:11 Every Jewish community is obligated to fast and to pray before G-d for every affliction that may come upon them. If it is not an appropriate time to fast, such as if they are being pursued and they are not permitted to fast in order to save their strength, then they should accept on themselves to fast for a certain number of days after they have been saved and it will be considered as if they fasted at the time of their trouble. We see this from Daniel 10:12, which tells us, "Then he said to me, 'Do not fear, Daniel, because your words were heard from the first day that you set your heart to understand and to fast before your G-d.' "

122:1 Because the afflictions of the destruction started on 17 Tamuz, some mourning practices are observed starting from that day and lasting until after Tisha b'Av. It is appropriate for every G-d-fearing person to say the prayers called Tikkun Chatzos during this period, each day after midday. We do not get married during this period - not even one who has not yet fulfilled his obligation to have children. Getting engaged - and even having the party - is permitted until Rosh Chodesh Av. From Rosh Chodesh on, even though one may still get engaged, the party is prohibited (even on Shabbos - Mishnah Brurah 551:16), though one may serve things like cakes. A Jew who earns his living by playing music may play for a non-Jew in order to earn money until Rosh Chodesh; it is prohibited from Rosh Chodesh until after Tisha b'Av. It is also prohibited on 17 Tamuz itself, as well as on 10 Teves. Some have the custom not to eat meat or drink wine from the 17 Tamuz until after Tisha b'Av except on Shabbos or at a meal celebrating a mitzvah. (One is not permitted to act stringently and refrain from meat even on Shabbos - MB 551:59.)