Is it permissible to impose a financial fine by agreement on whoever's phone rings in the mosque?

It is permissible to obligate the mosque's congregants to pay a financial fine to the mosque, if this is done with their consent and as a donation from them. This falls under the category of obligating a donation and charity with a condition, which is permissible according to some scholars. As for whoever does not agree to pay this fine, it is not obligatory upon them, and they do not incur sin by not paying it.