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