What is the evidence for the prohibition of posting advertisements and fatwas in mosques?

Question:
You issued a ruling in previous lessons prohibiting the posting of advertisements and fatwas in mosques. When I informed the imam of the mosque in my neighborhood, he said there is no evidence for this. Is there evidence for the prohibition of posting what was mentioned in mosques?

Answer:
I did not say it is forbidden; I said it is not befitting. This is what is not befitting to post in mosques, because mosques are not a place for posting advertisements and bulletins. It occupies the worshippers and opens the door for the ignorant and those who push matters onto people. They find themselves posting notices in the mosques, and they post superstitions in them.
Advertisements for religious innovations. Closing the door on this matter and keeping mosques away from such things is undoubtedly the most cautious and required course. Yes. And the one who tells you there is no evidence for this means he wants to be stubborn in his own way. He has become stubborn, so let him be as he is. You have conveyed the message to him, and that is enough. Yes.