Mu'awiyah bin Abi Sufian (RAA) narrated, 'The Messenger of Allah (ﷺ) said regarding the night of al-Qadr, "It is the 27th night (of Ramadan).'' Related by Abu Dawud. But it is most probably the saying of Mu'awiyah and not the Prophet (ﷺ). (ID)
English reference (ID): Book 5, Hadith 725 (ID)
Arabic reference (ID): Book 5, Hadith 705 (ID)