Musannaf Ibn Abi Shaybah

Hazrat Ata narrates that once Hazrat Abu Dharr was at a distance of three days' journey from the Holy Prophet (peace and blessings be upon him) when he became junub (in a state of major ritual impurity). Then he reached the presence of the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him), after finishing the Fajr prayer, went to relieve himself. Then he turned towards Hazrat Abu Dharr and struck his hands on the earth and wiped them over his face and palms.