While the Messenger of Allah ﷺ was leading his Companions in prayer, he took off his sandals and laid them on his left side; so when the people saw this, they removed their sandals. When the Messenger of Allah ﷺ finished his prayer, he asked: What made you remove your sandals? The replied: We saw you remove your sandals, so we removed our sandals. The Messenger of Allah ﷺ then said: Gabriel came to me and informed me that there was filth in them. When any of you comes to the mosque, he should see; if he finds filth on his sandals, he should wipe it off and pray in them.
بَيْنَمَا رَسُولُ اللَّهِ ﷺ يُصَلِّي بِأَصْحَابِهِ إِذْ خَلَعَ نَعْلَيْهِ فَوَضَعَهُمَا عَنْ يَسَارِهِ فَلَمَّا رَأَى ذَلِكَ الْقَوْمُ أَلْقَوْا نِعَالَهُمْ فَلَمَّا قَضَى رَسُولُ اللَّهِ ﷺ صَلاَتَهُ قَالَ مَا حَمَلَكُمْ عَلَى إِلْقَائِكُمْ نِعَالَكُمْ قَالُوا رَأَيْنَاكَ أَلْقَيْتَ نَعْلَيْكَ فَأَلْقَيْنَا نِعَالَنَا فَقَالَ رَسُولُ اللَّهِ ﷺ إِنَّ جِبْرِيلَ ﷺ أَتَانِي فَأَخْبَرَنِي أَنَّ فِيهِمَا قَذَرًا وَقَالَ إِذَا جَاءَ أَحَدُكُمْ إِلَى الْمَسْجِدِ فَلْيَنْظُرْ فَإِنْ رَأَى فِي نَعْلَيْهِ قَذَرًا أَوْ أَذًى فَلْيَمْسَحْهُ وَلْيُصَلِّ فِيهِمَا