Sahih 
Al Bukhari
صحيح البخاري
66
                Virtues of the Qur'an
كتاب فضائل القرآن
Chapter 1: How the Divine Revelation used to be revealed and what was the first thing revealed
باب كَيْفَ نُزُولُ الْوَحْىِ وَأَوَّلُ مَا نَزَلَ
Sahih Al Bukhari 4978, 4979
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.
حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُوسَى، عَنْ شَيْبَانَ، عَنْ يَحْيَى، عَنْ أَبِي سَلَمَةَ، قَالَ أَخْبَرَتْنِي عَائِشَةُ، وَابْنُ، عَبَّاسٍ رضى الله عنهم قَالاَ لَبِثَ النَّبِيُّ صلى الله عليه وسلم بِمَكَّةَ عَشْرَ سِنِينَ يُنْزَلُ عَلَيْهِ الْقُرْآنُ وَبِالْمَدِينَةِ عَشْرَ سِنِينَ.
Grade: Sahih 
  
                                        REFERENCE: Sahih Al Bukhari 4978, 4979
                        
In-book reference: Sahih Al Bukhari Book 66 Chapter 1 Hadith 1
                In-book reference: Sahih Al Bukhari Book 66 Chapter 1 Hadith 1

 
                    
                    