Section: Announcement of lost things in the mosque
184. Prayers for the person who announcing the lost thing in the mosque
Narrated Abu Hurairah: That the Messenger of Allah (ﷺ) said: "When you see someone announcing about something lost then say:
لَا رَدَّهَا اللَّهُ عَلَيْكَ
لَا رَدَّهَا اللّٰهُ عَلَيْكَ
laa raddahAllahu 'alaik
Translation
May Allah not return it to you.
This is because the mosques were not built for this purpose.
ReferenceSahih (Albani). Tirmidhi: 1321