Hadith 4:644
Ibn Idris narrated to us, from ‘Asim ibn Kulayb, from his father, from Ibn ‘Abbas, from ‘Umar, who said: You have certainly known that the Messenger of Allah (may Allah bless him and grant him peace) said regarding the Night of Decree: "Seek it in the last ten [nights]."
حدثنا بن إدريس عن عاصم بن كليب عن أبيه عن بن عباس عن عمر قال لقد علمتم أن رسول الله صلى الله عليه وسلم قال في ليلة القدر أطلبوها في العشر الأواخر