Question: What is the ruling on hanging posters for Knowledge-based lessons or study circles and prize winners and other than that inside the masjid? If it is allowed, how do we respond to the one who says: verily in these things are a prohibited means and it is announcing business-related things and other than that [in the masdji]?
Answer: “No, this is not announcing business-related things or buying or selling which is not allowed. Announcing lectures and seminars, this calling to good, calling to knowledge, this is something which the Masaajid were built for. The Masaajid were built for studying, teaching, prayer, remembering Allah. As for posters and business-related affairs, that is not allowed in the masjid”.
[Fatawa Munawwa’ah no. 10]
Faisal Ibn Abdul Qaadir Ibn Hassan