Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 485
Narated By 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 Apostle of Allah (pbuh) doing so.