Abu Hurayrah (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) saying: "Whoever announces a lost item in the mosque, say to him: May Allah not return your item to you, for mosques were not built for this."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20262