Sahih Ibn Khuzaymah

Abdullah bin Abdullah bin Khubaib narrates that during this month (the blessed month of Ramadan), we were sitting in the gathering of the Juhaina tribe with Sayyiduna Abdullah bin Anis (may Allah be pleased with him). We asked, "O Abu Yahya, have you heard anything from the Messenger of Allah (peace be upon him) about this blessed night?" He replied, "Yes. We were sitting with the Messenger of Allah (peace be upon him) in the last part of this month when a man asked him, 'When should we seek this blessed night?' He said: 'Seek it on the twenty-third night.' Then one of the people said, 'Then this night is the first of the eight nights.' Imam Abu Bakr (may Allah have mercy on him) says that the narrator whose name Ibn Ulayya did not mention is Abdullah bin Khubaib."

It is narrated from the companion of the Messenger of Allah, Abdullah bin Unais (may Allah be pleased with him), that he was asked about Laylat al-Qadr. He said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Seek it tonight." And it was the twenty-third night. So a man said: O Messenger of Allah, then this is the first of the eight nights. The Prophet (peace and blessings be upon him) said: "Rather, it is the first of the seven, because sometimes the month is not a complete thirty days."