كتاب الصلاة
2  
The Book of Prayer
Narrated [Abu Hurairah (RA)]:
Allah's Messenger (ﷺ) said: "Whoever hears a man crying out in the mosque about something he has lost, he should say, 'May Allah not restore it to you', for the mosques were not built for this." [Reported by Muslim].
وَعَنْهُ قَالَ : قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ مَنْ سَمِعَ رَجُلاً يَنْشُدُ ضَالَّةً فِي اَلْمَسْجِدِ فَلْيَقُلْ : لَا رَدَّهَا اَللَّهُ عَلَيْكَ , فَإِنَّ اَلْمَسَاجِدَ لَمْ تُبْنَ لِهَذَا } رَوَاهُ مُسْلِم ٌ 1


‏1 ‏- صحيح .‏ رواه مسلم (568)‏ .‏

Sunnah.com reference : Book 2, Hadith 128
English translation : Book 2, Hadith 254
Arabic reference : Book 2, Hadith 256