مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3101
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: I learned al-Muhkam at the time of The Messenger of Allah (ﷺ), and the Prophet (ﷺ) died when I was ten years old. I (the narrator) said to him: What is al-Muhkam? He said: Al-Mufassal.
Musnad Ahmad 3125Its isnad is saheeh, al-Bukhari (5036)]