Musnad Ahmad 937:16

Isma'il narrated to us, Ayyub narrated to us, from Abu Qilabah, from a man from Banu 'Amir, who said: I was a disbeliever, then Allah guided me to Islam. I used to stay away from water, and my family was with me, and major ritual impurity (janabah) would befall me, and that weighed heavily upon my soul. Abu Dharr had been described to me, so I performed Hajj and entered the mosque of Mina, and I recognized him by the description. There was an elderly man, lean and dark-skinned, wearing a Qatari garment. I went until I stood beside him while he was praying, and I greeted him, but he did not return the greeting to me. Then he prayed a prayer, completing it, perfecting it, and making it long. When he finished, he returned my greeting. I said: "Are you Abu Dharr?" He said: "My family claims that." He said: "I was a disbeliever, then Allah guided me to Islam, and my religion concerned me. I used to stay away from water, and my family was with me, and major ritual impurity would befall me, and that weighed heavily upon my soul." He said: "Do you know Abu Dharr?" I said: "Yes." He said: "I found the climate of Medina unsuitable" — Ayyub said: or a word similar to it — "so the Messenger of Allah (ﷺ) ordered for me a herd of camels and sheep, and I would be among them. I would stay away from water, and my family was with me, and major ritual impurity would befall me, and it occurred to me that I had perished. So I sat upon a camel of mine and reached the Messenger of Allah (ﷺ) at midday, while he was sitting in the shade of the mosque among a group of his companions. I dismounted from the camel and said: 'O Messenger of Allah, I have perished.' He said: 'And what has caused you to perish?' I told him, and he laughed. Then he called for someone from his household, and a black slave girl came with a wooden bowl containing water; it was not full, and it was sloshing about. I screened myself with the camel, and the Messenger of Allah (ﷺ) ordered a man from the people to screen me, so I performed ghusl. Then I came to him, and he said: 'Indeed, the pure earth is a means of purification as long as you do not find water, even if it be for ten years. But when you find water, then let it touch your skin.'"