Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

"I missed the Prophet (saw) one night, so I went out looking for him. I found him at Al-Baqi', raising his head towards the sky. He said: 'O Aishah, were you afraid that Allah and His Messenger would wrong you?'" She said: "I said: 'No, it is not that, but I thought that you had gone to one of your other wives.' He said: 'Allah descends on the night of the middle of Sha'ban to the lowest heaven, and He forgives more than the numbers of hairs on the sheep of Banu Kalb.'" Daif