This Halacha is an excerpt from our Sefer
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The Yartzeit of the Baal Shem Tov:
The Baal Shem Tov passed away on the 1st day of Shavuot in the year 5530. He was buried on the second day of Shavuos, the 7th of Sivan. For this reason, it is proper to say over a teaching and story of the Besht during Shavuos.
 Sefer Hasichos 1954 p. 140; Likkutei Dibburim 1:32; Likkutei Sichos 8:21
 See Likkutei Sichos 4:1031
 Sefer Hasichos 1944:140 that so is custom of Rabbeim; Toras Menachem 40:58 that since the Rebbe Rayatz told over this custom, it is proper that every person follow it.