And from the day on which you bring the sheaf of elevation offering—the day after the sabbath—you shall count off seven weeks. They must be complete: you must count until the day after the seventh week—fifty days; then you shall bring an offering of new grain to the LORD.

Rabbi Akiva says that the verse should be understood as follows: If one studied Torah in his youth he should study more Torah in his old age; if he had students in his youth he should have additional students in his old age, as it is stated: “In the morning sow your seed, etc.” They said by way of example that Rabbi Akiva had twelve thousand pairs of students in an area of land that stretched from Gevat to Antipatris in Judea, and they all died in one period of time, because they did not treat each other with respect. And the world was desolate of Torah until Rabbi Akiva came to our Rabbis in the South and taught his Torah to them. This second group of disciples consisted of Rabbi Meir, Rabbi Yehuda, Rabbi Yosei, Rabbi Shimon, and Rabbi Elazar ben Shamua. And these are the very ones who upheld the study of Torah at that time. Although Rabbi Akiva’s earlier students did not survive, his later disciples were able to transmit the Torah to future generations. With regard to the twelve thousand pairs of Rabbi Akiva’s students, the Gemara adds: It is taught that all of them died in the period from Passover until Shavuot. Rav Ḥama bar Abba said, and some say it was Rabbi Ḥiyya bar Avin: They all died a bad death. The Gemara inquires: What is it that is called a bad death? Rav Naḥman said: Askera (Diphtheria?).

The Gemara relates: When they took Rabbi Akiva out to be executed, it was time for the recitation of Shema. And they were raking his flesh with iron combs, and he was reciting Shema, thereby accepting upon himself the yoke of Heaven. His students said to him: Our teacher, even now, as you suffer, you recite Shema? He said to them: All my days I have been troubled by the verse: With all your soul, meaning: Even if God takes your soul. I said to myself: When will the opportunity be afforded me to fulfill this verse? Now that it has been afforded me, shall I not fulfill it? He prolonged his uttering of the word: One, until his soul left his body as he uttered his final word: One. A voice descended from heaven and said: Happy are you, Rabbi Akiva, that your soul left your body as you uttered: One.

The Gemara relates that this resulted due to an incident that took place when Rabbi Yehuda and Rabbi Yosei and Rabbi Shimon were sitting, and Yehuda, son of converts, sat beside them. Rabbi Yehuda opened and said: How pleasant are the actions of this nation, the Romans, as they established marketplaces, established bridges, and established bathhouses. Rabbi Yosei was silent. Rabbi Shimon ben Yoḥai responded and said: Everything that they established, they established only for their own purposes. They established marketplaces, to place prostitutes in them; bathhouses, to pamper themselves; and bridges, to collect taxes from all who pass over them. Yehuda, son of converts, went and related their statements to his household, and those statements continued to spread until they were heard by the monarchy. They ruled and said: Yehuda, who elevated the Roman regime, shall be elevated and appointed as head of the Sages, the head of the speakers in every place. Yosei, who remained silent, shall be exiled from his home in Judea as punishment, and sent to the city of Tzippori in the Galilee. And Shimon, who denounced the government, shall be killed.

Rabbi Shimon bar Yoḥai and his son, Rabbi Elazar, went and hid in the study hall. Every day Rabbi Shimon’s wife would bring them bread and a jug of water and they would eat. When the decree intensified, Rabbi Shimon said to his son: Women are easily impressionable and, therefore, there is room for concern lest the authorities torture her and she reveal our whereabouts.

They went and they hid in a cave. A miracle occurred and a carob tree was created for them as well as a spring of water. They would remove their clothes and sit covered in sand up to their necks. They would study Torah all day in that manner. At the time of prayer, they would dress, cover themselves, and pray, and they would again remove their clothes afterward so that they would not become tattered. They sat in the cave for twelve years.

Elijah the Prophet came and stood at the entrance to the cave and said: Who will inform bar Yoḥai that the emperor died and his decree has been abrogated? They emerged from the cave, and saw people who were plowing and sowing. Rabbi Shimon bar Yoḥai said: These people abandon eternal life of Torah study and engage in temporal life for their own sustenance. The Gemara relates that every place that Rabbi Shimon and his son Rabbi Elazar directed their eyes was immediately burned. A Divine Voice emerged and said to them: Did you emerge from the cave in order to destroy My world? Return to your cave. They again went and sat there for twelve months. They said: The judgment of the wicked in Gehenna lasts for twelve months. Surely their sin was atoned in that time.

A Divine Voice emerged and said to them: Emerge from your cave. They emerged. Everywhere that Rabbi Elazar would strike, Rabbi Shimon would heal. Rabbi Shimon said to Rabbi Elazar: My son, you and I suffice for the entire world, as the two of us are engaged in the proper study of Torah.

As the sun was setting on Shabbat eve, they saw an elderly man who was holding two bundles of myrtle branches and running at twilight. They said to him: Why do you have these? He said to them: In honor of Shabbat. They said to him: And let one suffice. He answered them: One is corresponding to: “Remember the Shabbat day, to keep it holy” (Exodus 20:8), and one is corresponding to: “Observe the Shabbat day, to keep it holy” (Deuteronomy 5:12).

Rabbi Shimon said to his son: See how beloved the mitzvot are to Israel. Their minds were put at ease and they were no longer as upset that people were not engaged in Torah study.

It is customary not to get married between Pesach and Shavuot, until Lag BaOmer (the 33rd day), because during that time, the students of Rabbi Akiva died. However, to do "erusin" and "kiddushin" (engagement and betrothal) is OK. And even for "nisuin" (marriage), if someone did so, we do not punish him. Rema: however, from Lag Ba'Omer onwards, all this is permitted (Abudraham, Beit Yosef & Minhagim). It is customary not to cut one's hair until Lag BaOmer, since it is said that that is when they stopped dying. One should not cut one's hair until the 34th day, in the morning, unless the 33rd day falls on Friday, in which case one may cut one's hair then, in honor of the Sabbath ("kavod Shabbat"). Rema: But in these countries, we do not follow the custom he advocates; rather, we cut our hair on the 33rd day, and we rejoice a bit, and we do not say Tachanun (Maharil and Minhagim). And one should only cut one's hair on the 33rd day itself, but not on its evening. However, if it falls on Sunday, our custom is to cut our hair on Friday in honor of the Sabbath (Maharil). Someone who is performing a brit milah (i.e., the sandak, mohel and the infant's father), or circumcizing his son, is allowed to cut his hair during sefirah in honor of the circumcision (Hagahot Minhagim).