(1) باب كَيْفَ نُزُولُ الْوَحْىِ وَأَوَّلُ مَا نَزَلَ
Narrated `Aisha and Ibn `Abbas:
The Prophet (ﷺ) remained in Mecca for ten years, during which the Qur'an used to be revealed to him; and he stayed in Medina for ten years.
Reference: Sahih al-Bukhari 4978, 4979
In-book reference: Book 66, Hadith 1
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 6, Book 61, Hadith 502