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  

That the Messenger of Allah ﷺ said: "When you see someone selling or buying in the Masjid then say: 'May Allah not profit your business.' And when you see someone announcing about something lost then say: 'May Allah not return it to you.'"  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا رَأَيْتُمْ مَنْ يَبِيعُ أَوْ يَبْتَاعُ فِي الْمَسْجِدِ فَقُولُوا لاَ أَرْبَحَ اللَّهُ تِجَارَتَكَ وَإِذَا رَأَيْتُمْ مَنْ يَنْشُدُ فِيهِ ضَالَّةً فَقُولُوا لاَ رَدَّ اللَّهُ عَلَيْكَ  

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  

The Messenger of Allah ﷺ prohibited buying and selling in the mosque, announcing aloud about a lost thing, the recitation of a poem in it, and prohibited sitting in a circle (in the mosque) on Friday before the prayer.  

أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ الشِّرَاءِ وَالْبَيْعِ فِي الْمَسْجِدِ وَأَنْ تُنْشَدَ فِيهِ ضَالَّةٌ وَأَنْ يُنْشَدَ فِيهِ شِعْرٌ وَنَهَى عَنِ التَّحَلُّقِ قَبْلَ الصَّلاَةِ يَوْمَ الْجُمُعَةِ  

I was standing in the mosque and somebody threw a gravel at me. I looked and found that he was ʿUmar bin Al-Khattab. He said to me, "Fetch those two men to me." When I did, he said to them, "Who are you? (Or) where do you come from?" They replied, "We are from Ta'if." ʿUmar said, "Were you from this city (Medina) I would have punished you for raising your voices in the mosque of Messenger of Allah ﷺ."  

مَنْ أَنْتُمَا أَوْ مِنْ أَيْنَ أَنْتُمَا قَالاَ مِنْ أَهْلِ الطَّائِفِ قَالَ لَوْ كُنْتُمَا مِنْ أَهْلِ الْبَلَدِ لأَوْجَعْتُكُمَا تَرْفَعَانِ أَصْوَاتَكُمَا فِي مَسْجِدِ رَسُولِ اللَّهِ ﷺ