HaRav S. Y. Chaim Kanievsky
Shikun Chazon Ish, Bnei Brak
BS"D 24 Iyar, 39 leMatmonin, 5780
To the Honored Rabbonim Geonim and Gabboim of Botei Knesses wherever they be, Hashem's blessings unto you for life:
Due to our numerous sins, we have been expelled from our shuls and botei medrash for these past many weeks, similar to that servant who comes to serve his master a drink but has that liquid thrown at his face. This is surely a sign from Heaven as a punishment for being lax in the respect due to a place of worship in that during the very prayers, cellphones are open and people are conversing through them.
This is a terrible defilement of prayer and of the sanctity of the beis knesses, which our ancestors never dreamed such a thing could happen, and which is totally against the Halochoh in Shulchan Oruch Orach Chaim 151 and in the Zohar Hakodosh (Vayakheil 205b) there are awesome things said about this.
Therefore, we must make a permanent takonoh that it is a strict prohibition (issur) to enter a beis knesses to pray with a cellphone that is not turned off and it should remain turned off for the duration of the tefillah. The gabboim have a responsibility to be vigilant and warn [the public] that this should be a rule that no one should violate.
It is also advisable that when we hopefully and speedily return to our botei knesses, that the various rabbonim strengthen and rouse [the public] with reinforcement, noting the severe prohibition to abuse or devalue the holiness of botei knesses and botei medrash.
In the merit of accepting these matters, may Hashem return us speedily to our worship of Him in permanent shuls and botei medrash, and receive our prayers with love and appeasement.
(signed) Chaim Kanievsky
Also one must be careful not to speak devorim beteilim in the beis haknesses.
(signed) Y. Gershon Edelstein