Sayyiduna Abu al-Juhaym (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) came from the direction of the well of Jamal, and a man met him (peace and blessings be upon him) and greeted him (peace and blessings be upon him), but he (peace and blessings be upon him) did not return his greeting until he (peace and blessings be upon him) came to a wall and wiped his face and hands; then he (peace and blessings be upon him) returned the greeting.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 990