Sunan Abi Dawud 484
Narrated Wathilah ibn al-Asqa':
AbuSa'id said: I saw Wathilah ibn al-Asqa' in the mosque of Damascus. He spat at the mat and then rubbed it with his foot. He was asked: Why did you do so? He said: Because I saw the Messenger of Allah (ﷺ) doing so.
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا الْفَرَجُ بْنُ فَضَالَةَ، عَنْ أَبِي سَعِيدٍ، قَالَ رَأَيْتُ وَاثِلَةَ بْنَ الأَسْقَعِ فِي مَسْجِدِ دِمَشْقَ بَصَقَ عَلَى الْبُورِيِّ ثُمَّ مَسَحَهُ بِرِجْلِهِ فَقِيلَ لَهُ لِمَ فَعَلْتَ هَذَا قَالَ لأَنِّي رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَفْعَلُهُ ‏.‏