It wasnarrated that 'Aishah said:
"When the Prophet (ﷺ) prayed thetwo (Sunnah) Rak'ah of Fajr, he would lie down on his right side." (ID)
English reference (ID): Vol. 1, Book 5, Hadith 1198 (ID)
Arabic reference (ID): Book 5, Hadith 1254 (ID)