'Aishah (May Allah be pleased with her) reported:
When the Prophet (ﷺ) had performed two Rak'ah before the Fajr prayer, he would lie down on his right side.[Al-Bukhari]. (ES)
App reference (ES): Book 9, Hadith 120 (ES)
Arabic/English book reference (ES): Book 9, Hadith 1110 (ES)