ASBI Pocket Beit Midrash: Aruch HaShulhan, Laws of Synagogue 151:1

(1) Synagogues and study halls have great holiness since we pray in them and learn in them Torah. These locations have a reflection of the sanctity of the Temple. Our wise ones of blessed memory said, "And these will be small Temples" (Megilah 29a)-these are the Synagogues and study halls. And this that is written, "O Lord, You have been our dwelling place throughout all generations"(Psalms 90:1)- these are the Synagogues and study halls. Even in the time of the destruction [of the Temple], they still have sanctity as it is written, "and I will desolate your sanctuaries" (Lev. 26:31)-"They are still sanctuaries even when they are desolate" (Megilah 28a). Therefore, Synagogues and study halls are not treated with lightheartedness, for example, with games, humor and small talk. The Arizal (R' Issac Luria) was very careful to only speak words of prayer in the Synagogue. Even words of rebuke should not be spoken, least it lead to the discussion of mundane matters. (Magen Avraham Subsection 3).