Q. The Mishna B’rura says that the reason, according to the Ramo, for joy on Lag BaOmer, is that the disciples of R. Akiva stopped dying on that day.
The custom is to behave with signs of mourning on the days on which they died. When they stopped dying, this mourning behavior should stop. But was their dying so part of the natural order of the day that a cessation of that “normal” is a cause for joy?
A. As can be seen from the Halachos and traditions of the days of Purim, Chanuka, Korban Todah,Birchas Hagomel, Seudas Hodoa and many others, whenever there was a gezeira or decree against our people, to the many or even to the single person, when they were saved Bechasdei Hashem, there is an obligation to thank Hashem accordingly and show him our greatest Hakoras Hatov and thankful recognition.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a