Yahya related to me from Malik from Nafi that she saw Safiyyabint Abi Ubayd, the wife of Abdullah ibn 'Umar, take off her head-covering and wipe her head with water. Nafi was a child at the time.Malik was asked about a man who did wudu but forgot to wipehis head until the water had dried. He said, "I consider that heshould wipe his head and then repeat the prayer if he has alreadyperformed it."Malik was asked about a man who did wudu butforgot to wipe his head until the water had dried. He said, "Iconsider that he should wipe his head and then repeat the prayer if hehas already performed it."
USC-MSA web (English) reference: Book 2, Hadith 41
Arabic reference: Book 2, Hadith 71