What is the omer? What is lag ba’omer and how is it connected to kabbalah/mysticism?
When we use the term omer, it usually refers to the commandment to count down the days from Passover until Shavuos — the anniversary of (i.e. the time in which we “re-experience”) the giving of the Torah on Mount Sinai. The counting is for those 7 weeks, and the fiftieth day is Shavuos (thus, the English name “Pentecost”). For over 1,500 years, this period was simply one of anticipation, and personal introspection, in preparation for the “re-experiencing of Sinai.” However, in the time following the destruction of the second temple, the 24,000 students of Rabbi Akiva (one of that generation’s leaders, revered as a Torah giant for all time) were Divinely punished by plague over 33 days of this period. Since then, part of this period has become one of mourning (i.e. one should not take a haircut, shave, or make a wedding), and there are various customs as to which 33 days to mourn. All agree, however, that none of the students died on the 33rd day, and the restrictions are, therefore, lifted from it. This day is called Lag Ba’Omer, simply meaning “33rd of the omer“.
Additionally, some decades after the tragedy of Rabbi Akiva’s students, Lag Ba’Omer took on new significance upon the passing of the great Torah sage and mystic, Rabbi Shimon bar Yochai. In your question, you mentioned kabbalah/mysticism. Well, Rabbi Shimon bar Yochai is actually the author of the Zohar, and, on his last day — the day that encompassed his entire life, he was capable of seeing grand, new secrets of kabbalah and was permitted to relay many of them to the world. This last day was Lag Ba’Omer.
Many people have a flaring interest for kabbalah, a lot of them with little or no knowledge of the basics of Torah and mitzvos — studies that take years and years to master. I must point out that trying to learn kabbalah without the proper background and training is very unrealistic — similar to trying to learn calculus II before calculus I. In fact, it is probably more accurately described as trying to learn trigonometry before knowing addition! But don’t worry, all of Torah is rich, meaningful, and, most importantly, real.
Best wishes,
Rabbi Azriel Schreiber