(26) بَابُ تَعَاهُدِ رَكْعَتَيِ الْفَجْرِ وَمَنْ سَمَّاهُمَا تَطَوُّعًا
Narrated `Aisha:
The Prophet (ﷺ) was never more regular and particular in offering any Nawafil than the two rak`at (Sunna) of the Fajr prayer.
Reference: Sahih al-Bukhari 1163
In-book reference: Book 19, Hadith 42
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 21, Hadith 260