The days between Pesaĥ and Shavu’ot are days of sorrow, because 24,000 of R. Akiva’s students died during that period. Therefore, we keep some customs of mourning during this period: we do not marry, get haircuts, or engage in elective dancing.

Before we discuss the details of these customs, let us expand a bit upon the main point, namely, the reason R. Akiva’s students died. The Talmud states:

R. Akiva had 12,000 pairs of students…and they all died during the same period, because they did not treat each other with respect…. It is taught in a beraita, “They all died between Pesaĥ and [Shavu’ot]…and they all died a terrible death.” The world was desolate until R. Akiva came to our rabbis in the south and taught them [and these are the new students]: R. Meir, R. Yehuda, R. Yose, R. Shimon, and R. Elazar b. Shamu’a; it was they who revived the Torah. (Yevamot 62b)

The Midrash (Bereishit Rabba 61:3) further recounts that R. Akiva said to his new students, “My sons, the first ones died only because they begrudged one another; make sure not to do as they did.”[1]

Since then, the omer period has become a time when some mourning customs are observed and when people, especially Torah students, try to improve their interpersonal relationships. Since this is based on custom, rather than an explicit rabbinic enactment, customs vary among the different Jewish communities, as we will explain below.

Around a thousand years later, during the time of the Crusades, which began in the year 4856 (1096), Christians slaughtered thousands of Jews in Germany. These tragedies, too, occurred mainly during the days of the omer. Approximately 500 years later, in 5408-5409 (1648-1649), the Jews were massacred once again, this time in Eastern Europe. Tens of thousands of Jews were murdered. These pogroms also occurred, for the most part, during the omer period. Therefore, Ashkenazim are inclined to be more stringent regarding these customs of mourning.