The Messenger of Allah ﷺ said: If anyone 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.  

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ سَمِعَ رَجُلاً يَنْشُدُ ضَالَّةً فِي الْمَسْجِدِ فَلْيَقُلْ لاَ رَدَّهَا اللَّهُ عَلَيْكَ فَإِنَّ الْمَسَاجِدَ لَمْ تُبْنَ لِهَذَا  

Abu Huraira reported Messenger of Allah ﷺ saying like this.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ بِمِثْلِهِ  

Who had called out for the red camel? Upon this the Messenger of Allah ﷺ said: May it not be restored to you! The mosques are built for what they are meant.  

مَنْ دَعَا إِلَى الْجَمَلِ الأَحْمَرِ فَقَالَ النَّبِيُّ ﷺ لاَ وَجَدْتَ إِنَّمَا بُنِيَتِ الْمَسَاجِدُ لِمَا بُنِيَتْ لَهُ  

Who called for a red camel? (Upon this) the Messenger of Allah ﷺ said: May it not be restored to you! The mosques are built for what they are meant.  

أَنَّ النَّبِيَّ ﷺ لَمَّا صَلَّى قَامَ رَجُلٌ فَقَالَ مَنْ دَعَا إِلَى الْجَمَلِ الأَحْمَرِ فَقَالَ النَّبِيُّ ﷺ لاَ وَجَدْتَ إِنَّمَا بُنِيَتِ الْمَسَاجِدُ لِمَا بُنِيَتْ لَهُ  

Ibn Buraida narrated it on the authority of his father that a Bedouin came when the Messenger of Allah ﷺ had completed the morning prayer. He thrust his head in the door of the mosque, and then the hadith (as narrated above) was narrated. This hadith has been reported by another chain of transmitters.  

جَاءَ أَعْرَابِيٌّ بَعْدَ مَا صَلَّى النَّبِيُّ ﷺ صَلاَةَ الْفَجْرِ فَأَدْخَلَ رَأْسَهُ مِنْ بَابِ الْمَسْجِدِ فَذَكَرَ بِمِثْلِ حَدِيثِهِمَا قَالَ مُسْلِمٌ هُوَ شَيْبَةُ بْنُ نَعَامَةَ أَبُو نَعَامَةَ رَوَى عَنْهُ مِسْعَرٌ وَهُشَيْمٌ وَجَرِيرٌ وَغَيْرُهُمْ مِنَ الْكُوفِيِّينَ