Sunan Ibn Majah Book 5, Hadith 1037

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا غُنْدَرٌ، عَنْ شُعْبَةَ، عَنِ النُّعْمَانِ بْنِ سَالِمٍ، عَنِ ابْنِ أَبِي أَوْسٍ، قَالَ كَانَ جَدِّي أَوْسٌ يُصَلِّي فَيُشِيرُ إِلَىَّ وَهُوَ فِي الصَّلاَةِ فَأُعْطِيهِ نَعْلَيْهِ وَيَقُولُ رَأَيْتُ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ يُصَلِّي فِي نَعْلَيْهِ ‏.‏

It was narrated that Ibn Abu Aws said:“My grandfather, Aws, used to perform prayer, and sometimes he would make a gesture while praying, and I would give him his sandals. He said: ‘I saw the Messenger of Allah (ﷺ) performing prayer in his sandals.’”