Musnad Ahmad 937:260

Yazid narrated to us, Hisham narrated to us, from Wasil, from Yahya ibn Aqil, from Yahya ibn Ya'mar, from Abu Dharr, from the Prophet, peace and blessings of Allah be upon him, who said: "My nation was presented to me with their deeds, the good and the bad. I saw among the good of their deeds the removal of harm from the road. And I saw among the bad of their deeds the phlegm in the mosque that is not buried."