Hazrat Ubayy (ra) memorised the Holy Quran after hearing every single word from the Holy Prophet (sa) himself. The Holy Prophet (sa) noticed his passion for learning and as a result paid special attention towards his education. The lofty rank and awe of prophethood would make even the most senior companions to abstain from asking [many] questions; however, Hazrat Ubayy (ra) would ask questions without hesitation. He would not ask questions unnecessarily; he paid due regard to the esteemed rank of prophethood and asked questions in a respectable manner, but he did not hesitate in doing so. Due to Hazrat Ubayy’s (ra) passion, sometimes the Holy Prophet (sa) would initiate the conversation himself without being prompted by a question.
(Sheikh Shah Moinuddin Ahmad Nadvi, Siyar al-Sahabah, Vol. 3 [Karachi, Pakistan: Dar al-Ishaah Urdu Bazar, 2004] 148)