Musnad Ahmad 928:17

Abdullah narrated to us, Muhammad ibn Abi Bakr al-Muqaddami, Khalaf ibn Hisham al-Bazzar, and Ubaydullah ibn Umar al-Qawariri narrated to me, they said: Hammad ibn Zayd narrated to us, Asim narrated to us, from Zirr, who said: I said to Ubayy ibn Ka’b: "O Abu al-Mundhir, inform me about the Night of Decree (Laylat al-Qadr), for our companion—meaning Ibn Mas’ud—used to say when asked about it: 'Whoever stands in prayer for the whole year will hit it.'" He said: "May Allah have mercy on Abu Abd al-Rahman. By Allah, he knew that it is in Ramadan, but he liked that they should not rely [solely on one night]. And it is the night of the twenty-seventh," and he did not make an exception. I said: "O Abu al-Mundhir, how did you know that?" He said: "By the sign which the Messenger of Allah, peace and blessings of Allah be upon him, told us: 'The morning of the Night of Decree, the sun rises without rays, as if it were a washbasin, until it rises.'" This is the wording of the hadith of al-Muqaddami.