Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever hears a person announcing a lost item in the mosque, let him say to him this (supplication) « لاَ أَدَّاھَا اللهُ عَلَيْكَ » May Allah not return it to you, for the mosques were not built for this purpose."