Musnad Ahmad 1153:1428

He said: I read to Abd al-Rahman: Malik, from Ibn Shihab, from Urwah ibn al-Zubayr, from Aisha, the wife of the Prophet, may God bless him and grant him peace, that the Messenger of God, may God bless him and grant him peace, prayed in the mosque, and people prayed with his prayer. Then he prayed the following night, and the people increased. Then they gathered on the third or fourth night, but the Messenger of God, may God bless him and grant him peace, did not come out to them. When morning came, he said: "I have seen what you did, and nothing prevented me from coming out to you except that I feared it would be made obligatory upon you." And that was in Ramadan.