Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 318
Narated By Ammar ibn Yasir : They (the Companions of the Prophet) wiped with pure earth (their hands and face) to offer the dawn prayer in the company of the Apostle of Allah (pbuh). They struck the ground with their palms and wiped their faces once. Then they repeated and struck the ground with their palms once again and wiped their arms completely up to the shoulders and up to the armpits with the inner side of their hands.