As mentioned above, the Rebbe placed a great emphasis on holding the upsherinish on the date of the child’s third birthday, not before and not afterwards. Nevertheless, there are occasions when because it is prohibited or customary not to cut hair the upsherinish should be postponed. They include:

a) Shabbos and festivals. The Rebbe writes1 the upsherinish should be held directly after the holy day, but not before.

b) Sefiras HaOmer, the Counting of the Omer. If the child’s birthday is before Lag BaOmer, the Rebbe writes that one could find rationales to allow the upsherinish to be held during the Counting of the Omer, although generally haircuts are not taken at this time. Nevertheless, since it is customary for children’s hair to be cut on Lag BaOmer, the upsherinish should be held at that time.2

If the child’s birthday is after Lag BaOmer, the upsherinish should be held on the day preceding Shavuos.3

c) Bein HaMetzarim, the Three Weeks between Tammuz 17 and Tishah BeAv It is also customary not to take haircuts during this time. The Rebbe writes4 that if a child’s birthday is between Rosh Chodesh Av and Tishah BeAv, the upsherinish should be held after the fast day.

With regard to a child whose birthday is between Tammuz 17 and Rosh Chodesh Av, we find a difference of opinion among the later halachic authorities. Kapos Temarim (sec. 14) states that the upsherinish should be postponed until after Tishah BeAv. Toras Yekusiel (Responsum 47), by contrast, rules that the upsherinish should be held on the child’s birthday.

d) Rosh Chodesh Rav Yehudah HaChossid5 advised that a person should not take a haircut on Rosh Chodesh. The Rebbe writes6 that a distinction could be made between a child’s first haircut which fulfills a significant Jewish custom and an ordinary haircut. Nevertheless, since an upsherinish is not an actual mitzvah, it is proper to postpone it until after Rosh Chodesh.