Musannaf Ibn Abi Shaybah

Hazrat Zubaid and Hazrat A'mash state that when Ibrahim would reach the door of the mosque and there was dung or something similar on his shoes or socks, he would clean it and then enter the mosque.

Hazrat Asim bin Munzir says that I asked Hazrat Urwah bin Zubair, "What is the ruling if dung gets on a shoe?" He replied, "Wipe it off and perform the prayer."

Hazrat Mas'ar says that I saw Hazrat Thabit bin Ubaid rubbing his shoe or his sock at the door of the mosque and he used to say that this is a means of purification.

Hazrat Hammad says that it was the practice of the predecessors that if moist dung got on the socks, they would clean it thoroughly.

Hazrat Abdul Kareem narrates that Hazrat Tawus greatly disliked it when, after entering the mosque, one did not clean their socks or shoes.