Musnad Ahmad 26:823

Shuja' ibn al-Walid narrated to us, Abu Khalid—who used to be among the Banu Dalan, Yazid al-Wasiti—narrated to us, from Talq ibn Habib, from Abu Aqrab al-Asadi, who said: I came to Abdullah ibn Mas'ud and found him on his *injaz*—meaning a roof. I heard him saying, "Allah and His Messenger have spoken the truth, Allah and His Messenger have spoken the truth." So I climbed up to him and said, "O Abu Abd al-Rahman, what is the matter with you that you say, 'Allah and His Messenger have spoken the truth, Allah and His Messenger have spoken the truth'?" He said, "The Messenger of Allah (peace and blessings of Allah be upon him) informed us that the Night of Decree (Laylat al-Qadr) is in the middle of the last seven nights, and that the sun rises on its morning without rays." He said: So I climbed up and looked at it, and I said, "Allah and His Messenger have spoken the truth, Allah and His Messenger have spoken the truth."