One must respect the holiness of shuls and yeshivos, for they are
considered miniature forms of the Beis Hamikdash. This means that one
should avoid joking and speaking idly in them.
The object of our fear and respect is not the holy place itself but rather
Hashem, who instructed us to fear it (Rambam, Hilchos Beis HaBechira
7:1). One should walk into a holy place with the awareness that Hashem's
presence is there (ibid., 5).
The Tosafos Yom Tov writes that in his days there were terrible massacres
in which thousands of Jews were killed. The sages of the time inquired
from Heaven to find out what caused these massacres, and they were
informed that it was due to inappropriate talking in shuls and yeshivos.
Because people are created in God's image, their words can have a great
impact on the world. If we misuse our gift of speech, our words can cause
great harm. May Hashem spare us and help us to improve our ways.