It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that some animals of booty gathered with the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "O Abu Dharr, go out into the desert with them." So I went out into the desert to al-Rabadhah. I would become junub and remain so for five or six days. Then I came to the Messenger of Allah (peace and blessings be upon him) and he (peace and blessings be upon him) said: "Abu Dharr!" I remained silent. He (peace and blessings be upon him) said: "O Abu Dharr, may your mother lose you; woe to your mother!" He (peace and blessings be upon him) called for a slave-girl, and she brought a large vessel of water. She screened me with my garment and I screened myself with the mount, then I took a ritual bath, and it was as if a mountain had been lifted off me. He (peace and blessings be upon him) said: "Clean earth is the ablution (wudu) of the Muslim, even if it be for ten years; and when you find water, let it touch your skin, for that is better."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1050