Musnad Abu Ya'la al-Mawsili 105:18

Abu Musa al-Harawi narrated to us, Abu Bakr ibn Ayyash narrated to us, from Abu Ishaq al-Hamdani, from Najiyah al-Anazi, who said: Ammar and Abdullah ibn Mas’ud began discussing tayammum (dry ablution). Abdullah said: "If I were to remain for a month without finding water, I would not pray." Ammar said to him: "Do you not remember when you and I were with the camels and became in a state of major ritual impurity (janabah)? I rolled in the dust just as an animal rolls. When I returned to the Messenger of Allah (peace be upon him) and informed him of what I had done, he said: 'It would have been sufficient for you to perform tayammum.'"