It is a widespread Jewish custom not to hold weddings, or celebrations that include dancing, and not to get haircuts during the days of the Omer. This is due to the mourning over the 24,000 students of Rabbi Akiva who died during this time because they did not treat each other with proper respect. According to Sephardic custom, these restrictions apply from the beginning of the Omer until the morning of the 34th day of the Omer. Among Ashkenazim, many observe the restrictions throughout the Omer (except on Lag B’Omer) and permit from Rosh Chodesh Sivan or from the morning of the 3rd of Sivan.
According to Chabad custom, the restrictions apply during the Omer, and haircuts are taken on the eve of Shavuot. However, weddings may be held in the three days before Shavuot. Chabad custom also includes not reciting the blessing "Shehecheyanu" during this period, so as not to make a blessing of joy specifically related to “this time” ("Who has granted us life, sustained us, and enabled us to reach this time"). However, the Shehecheyanu blessing is recited on Shabbat and Lag B’Omer.
That said, even for those who observe this custom, one only needs to refrain from things that would require the Shehecheyanu blessing (since the concern is about saying this particular blessing). Therefore, for household items, which do not require this blessing, there is no prohibition, and one may purchase such items during the Omer. Buying a home should ideally be avoided, and a new garment should be worn for the first time on Shabbat or Lag B’Omer.
Translated and Adapted from Sichat HaShevua
