مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2343
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn ‘Abbas that the Prophet (ﷺ) came to them quickly, and we got worried because of his rushing. When he reached us he said: “I came rushing to tell you about Lailatal-Qadr, but then I was caused to forget it whilst I was coming to you. However seek it in the last ten nights of Ramadan."
Musnad Ahmad 2352lts isnad is saheeh, see the previous report]