Section: Announcement of lost things in the mosque
184. Dua for the one who announces lost items 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