It was said that R. Akiva had twelve thousand pairs of disciples, from Gabbat to Antipatris; and all of them died at the same time because they did not treat each other with respect. The world remained desolate until R. Akiva came to our Masters in the South and taught the Torah to them. These were R. Meir, R. Yehuda, R. Yossi, R. Shimon and R. Elazar ben Shammua, and it was they who revived the Torah at that time. A Tanna taught: All of them died between Pesaḥ and Shavuot. R. Ḥamma b. Abba or, some say, R. Ḥiyya b. Abin said: All of them died a cruel death. What was it? R. Naḥman replied: Diphtheria. (Yevamot 62b)
Kohelet Rabba and Bereishit Rabba record the same story, but only mention that they died “during the same period,” and they attribute their death to “being stingy with their Torah” (lefi she’einehem tzara). R. Akiva urged his new students not to behave in such a manner, and in turn, “the world was filled with Torah.”
Based on the Gemara, the Geonim (Shaarei Teshuva 278) cite an ancient custom of observing certain mourning customs between Pesacḥ and Shavuot (referred to as “Atzeret”). In the Middle Ages, the Rishonim attributed other reasons to these mourning practices. Some ascribe the mourning practices to the precarious state of the Jewish people during this period, as they pray that God judges the world favorably (Abudraham, Tefillot Pesaḥ; Rabbeinu Yeruḥam, Toldot Adam VeḤava 1:5). Thus, these practices are intended to arouse teshuva, and not necessarily as an expression of mourning. Others attribute these minhagei aveilut to the destruction of the flourishing Jewish communities of France and Germany during the Crusades (eleventh and twelfth centuries). The Sefer Assufot (thirteenth-century Germany), for example, records that “people do not marry between Pesaḥ and Atzeret; this is because of the pain of the decrees, that the communities were killed in this entire kingdom.” Taz (493:2) and the Arukh HaShulḥan (493:1) cite this reason as well.
Similarly, Rabbi Yaakov Emden writes in his Siddur Beit Yaakov, “R. Akiva’s students died and, due to our many sins, a number of communities were destroyed at the same time of year during the Crusades in Ashkenaz, and in 5408 in Poland.” The latter refers to the Chmielnicki massacres, which took place in the spring of 1648. Although some have objected to the observance of Yom HaShoah, the day of commemoration for the murder of six million Jews during the Holocaust, because it falls during the festive month of Nisan, these sources may indicate that remembering tragedies that befell the Jewish people specifically during the period of Sefirat HaOmer has its precedents.
Although many sources indicate that we observe certain minhagei aveilut during this period, the Rambanasserts that the days between Pesacḥ and Shavuot are actually similar to Chol HaMo’ed:
And you should count forty-nine days, and seven weeks, and sanctify the eighth day, like the eighth day of Sukkot, and these days which are counted in between are akin to Chol HaMo’ed, between the first and eighth of a festival…and that is why our Rabbis refer to Shavuot as “Atzeret” (a day of cessation), as it is similar to the eighth day of Sukkot, which is called “Atzeret.”(Lev. 23:36)
The Rambanviews Pesacḥ as the first festive day, Shavuot as the last day, and the entire interim period as a quasi–Chol-HaMoed. These days are thus fundamentally days of excitement, anticipation, and happiness leading up to the giving of the Torah on Shavuot.
Are the days of the Omer days of mourning or joy? I would like to suggest that while the period of Bein HaMetzarim between Shiva Asar B’Tammuz and Tisha B’Av is categorically defined as a one of mourning, the days of Sefirat HaOmer, however, are quite different. One must strike a balance between the customary mourning practices – reminding us of the behavior that led to the death of R. Akiva’s students, which was antithetical to the unity the Jewish people displayed before receiving the Torah (Rashi, Ex. 19:2) – and the festive nature of the period, as described by Ramban. If we internalize these messages we will be worthy of receiving the Torah, and celebrating in the fullest sense the festival of Shavuot.