Abu Ahwas reported,

We were in the house of Abu Musa with a group of the companions of Abdullah, and they were examining a copy of the Quran. Abdullah stood up, and Abu Masud said, "I do not know of anyone the Messenger of Allah left behind who is more knowledgeable about what Allah revealed than this man who has just stood."Abu Musa said, "If you say that, indeed he used to be present when we were absent, and he was granted permission to enter when we were kept out."

Azami 10268

Sahih

عن أبي الأحوص قال

كنا في دار أبي موسى مع نفر من أصحاب عبد الله، وهم ينظرون في مصحف، فقام عبد الله فقال أبو مسعود: ما أعلم رسول الله ترك بعده أعلم بما أنزل الله من هذا القائم، فقال أبو موسى: أما لئن قلت ذاك، لقد كان يشهد إذا غبنا، ويؤذن له إذا حجينا.

الأعظمي 10268صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Virtues of the Companions and reports about them
Chapter
Virtues of individual Companions and their reports
Section
Virtues of Abdullah bin Masud
Numbering
Jami al-Kamil 10268 (2nd edition)
Azami 10268