From Sahih Muslim (Hadith 1902):
Ibn 'Abbas reported Allah's Messenger (ﷺ) as saying:Gabriel taught me to recite in one style. I replied to him and kept asking him to give more (styles), till he reached seven modes (of recitation). Ibn Shibab said: It has reached me that these seven styles are essentially one, not differing about what is permitted and what is forbidden
Reference: Muslim 1902