Sunan At-Tirmidhi

Narrated Abu 'Abdur-Rahman:from 'Uthman bin 'Affan that the Messenger of Allah (ﷺ) said: ""The best of you is he who learns the Qur'an and teaches it."" Abu 'Abdur-Rahman said: ""So that is why I sit at this seat of mine."" And he taught the Qur'an during the time of 'Uthman until Al-Hajjaj bin Yusuf came. (Sahih)