مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2700
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
Ibn 'Abbas (رضي الله عنه) narrated that the Messenger of Allah (ﷺ) said: "Jibreel (عليه السلام) taught me the Qur'an with one mode of recitation but I asked him to recite it in another way and I kept asking him for more and he taught me more, until he ended up teaching me seven modes of recitation.”
Musnad Ahmad 2717Its isnad is saheeh]