Hadithcore
Mishkat al-Masabih, 1190

She said that when the Prophet (ﷺ) prayed the two <i>rak'as</i> of the dawn prayer he lay down on his right side. (Bukhari and Muslim.)

وَعَنْهَا قَالَتْ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا صَلَّى رَكْعَتَيِ الْفَجْرِ اضْطَجَعَ عَلَى شقَّه الْأَيْمن "

References1 variant
In-Book Reference
Book 4, Hadith 606