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.