(22) باب الْمُدَاوَمَةِ عَلَى رَكْعَتَىِ الْفَجْرِ
Narrated `Aisha;:
Allah's Messenger (ﷺ) offered the `Isha' prayer (and then got up at the Tahajjud time) and offered eight rak`at and then offered two rak`at while sitting. He then offered two rak`at in between the Adhan and Iqama (of the Fajr prayer) and he never missed them.
Reference: Sahih al-Bukhari 1159
In-book reference: Book 19, Hadith 38
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 21, Hadith 256