Is it permissible to allow non-Muslims to enter mosques for visitation?

There is no harm in a disbeliever entering a mosque for a legitimate and permissible purpose, such as listening to a sermon or drinking water. The Prophet indeed hosted disbelieving delegations in his mosque so they could observe the worshippers and hear his recitation and sermons. He also tied Thumamah ibn Uthal in the mosque until he embraced Islam. However, the entry of tourist groups for sightseeing, dressed immodestly and carrying cameras without showing respect, is a reprehensible act that should not be permitted.