Musannaf Ibn Abi Shayba 3:6290

Marwan ibn Mu'awiyah narrated to us, from Qanan ibn Abdullah al-Nahmi, who said: I asked Zirr about the Night of Decree (Laylat al-Qadr). He said: Umar, Hudhayfah, and a group of the companions of the Messenger of Allah (may Allah bless him and grant him peace) did not doubt that it is the night of the twenty-seventh, with three [nights] remaining. Zirr said: So I observed it continuously.