مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2586
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 ten years old and had recently been circumcised, and I had read al-Muhkam of the Qur'an. I (the narrator) said to Abu Bishr: What is al-Muhkam? He said: al-Mufassal.
Musnad Ahmad 2601Its isnad is saheeh]