Q) What is the ruling on displaying advertisements in the Masjid about competitions, lectures or Islamic seminars, under the auspices of specific companies or schools?
A) Praise be to Allaah.
Mosques are for worship, and it is forbidden to buy, sell and earn money therein. So it is not permissible to use the mosque as a means of advertising for companies, schools or anything else.
As for advertisements about religious lectures and seminars, there is nothing wrong with that, so long as that is not an advertisement for a specific committee, company, institution or the like. End quote.
From Fataawa al-Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah Aal al-Shaykh (Majallat al-Da’wah, 43)