Musannaf Ibn Abi Shayba 17:1047

Yazid ibn Harun narrated to us, he said: Hisham ibn Hassan informed us, from Wasil, the freed slave of Abu 'Uyaynah, from Yahya ibn 'Aqil, from Yahya ibn Ya'mar, from Abu Dharr, from the Prophet, may Allah bless him and grant him peace, who said: "My nation was presented to me with their deeds, their good ones and their bad ones. I saw among their good deeds the removal of an obstacle from the road. And I saw among their bad deeds the phlegm in the mosque that is not buried."