مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3521
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) died when I was fifteen years old.
Musnad Ahmad 3543lts isnad is saheeh, al-Bukhari (5035)]