‘Alee al Madeenee stated:
"Masrooq said: ' I studied the companions of the Messenger, صلى الله عليه وسلم,and found that their knowledge ended with six individuals;
'Umar ibn al Khataab
'Alee ibn Abee Taalib
‘Abdullaah ibn Mas’ood
Abu ad Dardaa
Ubay ibn Ka'b and
Zayd ibn Thaabit.
I further studied these six and found that their knowledge ended with two of them; 'Alee and 'Abdullaah.[1]
Al Khateeb al Baghdadee narrated upon the authority of Masrooq ibn al Ajda' al Hamdanee who said:
"The scholars after their Prophet, صلى الله عليه وسلم, were six, those who used to give verdicts that people acted upon, determine the amount of wealth to be inherited, practice Sunan that were acted upon, they were:
'Umar ibn al Khataab
'Alee ibn Abee Taalib
'Abdullaah ibn Mas'ood
Ubay ibn Ka'b
Zayd ibn Thaabit
Abu Musa al Ash'aree
He then said:
"Of these six, three were in al Kufah; 'Alee, 'Abdullaah and Abu Musa, the other three were spread out."
'Alee al Madeenee also narrated on the authority of Masrooq who said:
"I studied the companions of the Messenger, صلى الله عليه وسلم, they were like al Akhaadh, amongst them were those who narrated to one person, amongst them were those who narrated to two and three, amongst them were those who narrated to everybody [i.e. everybody took narrations from them].
'Abdullaah ibn Mas'ood was amongst those who narrated to everybody.”