I asked Ibn 'Umar about the gravel spread pin the mosque. He replied: One night the rain fell and the earth was moistened. A man was bringing the gravel (broken stones) in his cloth and spreading it beneath him. When the Messenger of Allah ﷺ finished his prayer, he said: How fine it is !  

مُطِرْنَا ذَاتَ لَيْلَةٍ فَأَصْبَحَتِ الأَرْضُ مُبْتَلَّةً فَجَعَلَ الرَّجُلُ يَأْتِي بِالْحَصَى فِي ثَوْبِهِ فَيَبْسُطُهُ تَحْتَهُ فَلَمَّا قَضَى رَسُولُ اللَّهِ ﷺ الصَّلاَةَ قَالَ مَا أَحْسَنَ هَذَا  

It was said that when a man removed gravels from the mosque, they adjured him.  

يُقَالُ إِنَّ الرَّجُلَ إِذَا أَخْرَجَ الْحَصَى مِنَ الْمَسْجِدِ يُنَاشِدُهُ  

The gravels adjure the person when removes them from the mosque.  

أَبُو بَدْرٍ أُرَاهُ قَدْ رَفَعَهُ إِلَى النَّبِيِّ ﷺ قَالَ إِنَّ الْحَصَاةَ لَتُنَاشِدُ الَّذِي يُخْرِجُهَا مِنَ الْمَسْجِدِ