(23) باب الضِّجْعَةِ عَلَى الشِّقِّ الأَيْمَنِ بَعْدَ رَكْعَتَىِ الْفَجْرِ
Narrated `Aisha:
The Prophet (ﷺ) used to lie down on his right side, after offering two rak`at (Sunna) of the Fajr prayer.
Reference: Sahih al-Bukhari 1160
In-book reference: Book 19, Hadith 39
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 21, Hadith 257