مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3378
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: The Messenger of Allah (ﷺ) said: “Seek Łuilatul-Qadr in the last ten nights (of Ramadan), when there are nine days left, or five days left, or seven days left."
Musnad Ahmad 3401Its isnad is saheeh, al-Bukhari (2021)]