Sahih al-Bukhari 813

It is related that Abu Salama said, "I went to Abu Sa'id al-Khudri and said, 'Could you not come out with us to the palm trees and talk to us.' He came out." He said, "I said, 'Relate to me what you heard from the Prophet, may Allah bless him and grant him peace, about the Night of Power.' He said, 'The Messenger of Allah, may Allah bless him and grant him peace, went into retreat (i'tikaf) during the first ten nights of Ramadan and we went into retreat with him. Jibril came to him and said, 'That which you are seeking is still to come.' Then he went into retreat for the middle ten days and we went into retreat with him. Jibril came to him and said, 'That which you are seeking is still to come.' The Prophet, may Allah bless him and grant him peace, got up to speak on the morning of the 20th of Ramadan and said, 'Whoever has been doing retreat with the Prophet, may Allah bless him and grant him peace, should continue. I was shown the Night of Power but I have forgotten it. It is an odd night among the last ten days. I dreamed that it was as if I was doing sajda in mud and water.' The roof of the mosque was made of palm branches and we could not see anything in the sky. Then suddenly a cloud came and it rained on us. The Prophet led us in the prayer until we could see the traces of mud and water on the forehead and on the tip of the nose of the Messenger of Allah, may Allah bless him and grant him peace, which was the confirmation of his dream."