It was narrated from Abu ,Abdullah, the freed slave of Shaddad bin Had…. that he heard Abu Hurairah (RA) say: "I heard the Messenger of Allah ﷺ say: "Whoever hears a man making a lost-and-found announcement in the Masjid, let him say: "May Allah not return it to you!" For the Masjids were not built for that." (Sahih)