Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1959
'Ubaidullah b. Anas b. Malik heard (his father) Anas b. Malik as saying: A bedouin came to the Messenger of Allah (may peace be upon him) on Friday as he was (delivering the sermon on his) pulpit; and the rest of the hadith is the same but with this addition:" I saw the cloud clearing just as a sheet is folded."