Yahya related to me from Malik that he had heard that Jabir ibnAbdullah al-Ansari was asked about wiping over a turban. He said, "Notunless you have wiped over your hair with water." (IT)
USC-MSA web (English) reference: Book 2, Hadith 39 (IT)
Arabic reference (IT): Book 2, Hadith 69 (IT)