Lag Ba'Omer 101

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.

And because of this - that it is [the] essence of Israel, and because of it were they redeemed and went up to all of the greatness to which they rose - we were commanded to tally from the morrow of the holiday of Pesach until the day of the giving of the Torah; to show about ourselves the great desire [we have] for the the honored day, which our hearts yearn [for] like 'a slave seeks shade' and always tallies when will come the yearned time that he goes out to freedom. As the tally shows about a man that all of his deliverance and all of his desire is to reach that time. And that which we count to the omer, meaning, "Such and such days have passed from the tally," and we do not tally "Such and such days do we have to the time," is because all of this shows us the great desire to reach the time [of Shavuot]...

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.

...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...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.