It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): Abu Aqrab al-Asadi (may Allah have mercy on him) said: I came to Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) while he was sitting on the roof of an upper room, and I too sat there with him. He was repeatedly saying: "Allah and His Messenger spoke the truth, Allah and His Messenger spoke the truth." He said that the Messenger of Allah (peace and blessings be upon him) had informed us: "Laylat al-Qadr is in the middle of the last seven days (of Ramadan), and its sign is that on its morning the sun rises in such a state that it has no rays (no dazzling brightness)." (Abu Aqrab (may Allah have mercy on him) said:) So I climbed up high and looked, and found the sun just as had been described, whereupon I too said: "Allah and His Messenger spoke the truth."
Hadith Referenceمسند أبي يعلى الموصلي / مسند عبد الله بن مسعود / 5371
Hadith Takhrij«قال سعيد بن محمد السناري: صحيح: المرفوع منه فقط» «أخرجه مسند أحمد برقم: 4361، مسند ابویعلیٰ ترقیم الاثری: 5349»