Musnad Ahmad 507:2

Hassan ibn Musa narrated to us, Ibn Lahi'ah narrated to us, Abd al-Rahman al-A'raj narrated to us, he said: I heard Umayr, the freed slave of Ibn Abbas, say: I and Abdullah ibn Yasar, the freed slave of Maymunah, the wife of the Prophet, may Allah bless him and grant him peace, came and entered upon Abu Juhaym ibn al-Harith ibn al-Simmah al-Ansari. Abu Juhaym said: "The Messenger of Allah, may Allah bless him and grant him peace, came from the direction of Bi'r Jamal. A man met him and greeted him, but the Messenger of Allah, may Allah bless him and grant him peace, did not return the greeting to him until he turned to a wall, wiped his face and his hands, and then the Messenger of Allah, may Allah bless him and grant him peace, returned the greeting to him."