Yahya related to me from Malik from Yazid ibn Abdullah ibn al-Hadi from Muhammad ibn Ibrahim al-Harith at-Taymi from Abu Salama ibnAbd ar-Rahman that Abu Said al-Khudri said, "The Messenger of Allah,may Allah bless him and grant him peace, used to do itikaf in themiddle ten days of Ramadan. One year he was doing itikaf and then,when it came to the night of the twenty-first, which was the nightbefore the morning when he would normally have finished his itikaf, hesaid, 'Whoever has done i'tikaf with me should continue doing itikaffor the last ten days. I saw a certain night and then I was made toforget it. I saw myself prostrating the following morning in water andclay. Look for it in the last ten days, and look for it on the odddays.' "Abu Said continued, "The sky poured with rain thatnight and the mosque had a roof (made of palm fronds) and the mosquewas soaked. With my own eyes I saw the Messenger of Allah, may Allahbless him and grant him peace, leave with traces of water and clay onhis forehead and nose, in the morning after the night of the twenty-first."
USC-MSA web (English) reference: Book 19, Hadith 10
Arabic reference: Book 19, Hadith 700