Sahih Bukhari: Hadith 4803

Once `Abdullah bin Mas`ud delivered a sermon before us and said, "By Allah, I learnt over seventy Suras direct from Allah's Messenger (ﷺ) . By Allah, the companions of the Prophet (ﷺ) came to know that I am one of those who know Allah's Book best of all of them, yet I am not the best of them." Shaqiq added: I sat in his religious gathering and I did not hear anybody opposing him (in his speech).