Hilchos Lashon Hara, Opening – positive commands (7)
If one speaks lashon hara in a beis hamedrash or shul, one transgresses the positive command of (Vayikra 19:30), “You shall fear My temple [mikdashi],” and our beis medrash too is considered a mikdash. Therefore, one may not make financial calculations in a shul, excepting for those of a mitzvah such as of the charity box, how much more is laughter and empty talk forbidden, and how much for is it forbidden to speak lashon hara and rechilus inside them.
Even people learning on a permanent basis in a beis medrash who are permitted to eat and drink there, transgress, “You shall fear My temple,” if they speak words of levity and frivolity, lashon hara or rechilus.