Hadith 1110
'Aishah (May Allah be pleased with her) reported:
عن عائشة رضي الله عنها قالت: كان النبي صلى الله عليه وسلم إذا صلى ركعتي الفجر، اضطجع على شقه الأيمن. ((رواه البخاري)).
When the Prophet (ﷺ) had performed two Rak'ah before the Fajr prayer, he would lie down on his right side. [Al-Bukhari].
In plain words
Aishah reports that after praying the two units before the dawn prayer, the Prophet would lie down on his right side, a small habit he kept.
Reference : Riyad as-Salihin 1110 In-book reference : Book 8, Hadith 120