I saw the Prophet ﷺ praying on the day of the conquest of Mecca and he had placed his shoe at his left side.  

رَأَيْتُ النَّبِيَّ ﷺ يُصَلِّي يَوْمَ الْفَتْحِ وَوَضَعَ نَعْلَيْهِ عَنْ يَسَارِهِ  

‘Abd Allah b. al-Sa’ib said; the Messenger of Allah ﷺ led us in the morning prayer at Mecca. He began to recite Surah al-Mu;minin and while he came to description of Moses and Aaron or the description of Moses and Jesus the narrator Ibn ‘Abbad doubts or other narrators differed amongst themselves on this word the prophet ﷺ coughed and gave up (recitation) and then bowed ‘Abd Allah b. al-Sa’ib was present seeing all this incident.  

صَلَّى بِنَا رَسُولُ اللَّهِ ﷺ الصُّبْحَ بِمَكَّةَ فَاسْتَفْتَحَ سُورَةَ الْمُؤْمِنِينَ حَتَّى إِذَا جَاءَ ذِكْرُ مُوسَى وَهَارُونَ أَوْ ذِكْرُ مُوسَى وَعِيسَى ابْنُ عَبَّادٍ يَشُكُّ أَوِ اخْتَلَفُوا أَخَذَتْ رَسُولَ اللَّهِ ﷺ سُعْلَةٌ فَحَذَفَ فَرَكَعَ وَعَبْدُ اللَّهِ بْنُ السَّائِبِ حَاضِرٌ لِذَلِكَ  

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  

This tradition has also been transmitted through a chain by Bakr b. ‘Abd Allah. This version has the word Khubuth (filth) and in two places the word Khubuthan (filth).  

عَنِ النَّبِيِّ ﷺ بِهَذَا قَالَ فِيهِمَا خَبَثًا قَالَ فِي الْمَوْضِعَيْنِ خَبَثًا  

The Messenger of Allah ﷺ said: Act differently from the Jews, for they do not pray in their sandals or their shoes.  

قَالَ رَسُولُ اللَّهِ ﷺ خَالِفُوا الْيَهُودَ فَإِنَّهُمْ لاَ يُصَلُّونَ فِي نِعَالِهِمْ وَلاَ خِفَافِهِمْ  

I saw the Messenger of Allah ﷺ praying both barefooted and wearing sandals.  

رَأَيْتُ رَسُولَ اللَّهِ ﷺ يُصَلِّي حَافِيًا وَمُنْتَعِلاً