It is proper to abstain from reciting the “Shehecheyanu” blessing during the three weeks between the Seventeenth of Tammuz and the Ninth of Av on a new fruit or a new garment. One should leave the new fruit or garment for after Tisha Be’av rather than to eat the fruit or wear the garment without reciting “Shehecheyanu.”
The source for this custom can be found in the Sefer Chassidim who writes that they would not eat a new fruit during the “Three Weeks,” for how can one recite the blessing of “Who has given us life, sustained us, and allowed us to reach this time,” during such a tragic period? Maran Ha’Shulchan Aruch likewise writes that it is preferable to abstain from reciting the “Shehecheyanu” blessing on a new fruit or garment during the “Three Weeks.” Rabbeinu Ha’Ari z”l rules likewise, as do the consensus of the Acharonim. (Chazon Ovadia-Arba Ta’aniyot, page 129)
If a pregnant woman sees a new fruit during the “Three Weeks” and craves it, she may indeed eat this fruit during this time and she should recite the “Shehecheyanu” blessing before eating it.
On Shabbatot that fall out during the “Three Weeks,” one may recite “Shehecheyanu” on a new fruit or garment. Nevertheless, following Rosh Chodesh Av, it is preferable to abstain from reciting “Shehecheyanu” on a new garment even on Shabbat. However, regarding reciting the “Shehecheyanu” blessing on a new fruit on the Shabbat following Rosh Chodesh Av, one may be lenient and do so. (See Responsa Yechave Da’at, Volume 1, Chapter 37)
One may purchase new clothing during the “Three Weeks” until Rosh Chodesh Av; nevertheless, the garments should not be worn until after Tisha Be’av.
Some customarily do not hold any weddings from the Seventeenth of Tammuz until the Ninth of Av, which is referred to as the “Three Weeks,” as we have already explained. This was indeed the custom in Ashkenazi countries.
The Sephardic custom in the holy city of Jerusalem, however, is to allow weddings to be held during this period, until the day of Rosh Chodesh Av. Nevertheless, beginning from Rosh Chodesh Av, although according to the letter of the law one who has not yet performed the Mitzvah of bearing children may indeed be lenient and get married, the custom is not to hold weddings at this time, for it is ominous to celebrate and be joyful at a time when the rest of the Jewish people are steeped in deep mourning.
Although the custom is to abstain from holding weddings from the day following Rosh Chodesh Av (which Ashkenazim customarily abstain from during the entire “Three Week” period), nevertheless, if one divorced one’s wife and, with the help of the intervention of a third party, the couple decides to remarry, this wedding may be held even after Rosh Chodesh Av, for it is not a source of great happiness. On the contrary, sometimes postponing such a wedding can cause whatever peace was restored to be lost and the entire remarriage proposal may thus fall through.