إِذَا صَلَّى أَحَدُكُمْ رَكْعَتَيِ الْفَجْرِ فَلْيَضْطَجِعْ عَلَى يَمِينِهِ (Tirmidhi: 420)
Meaning: When one of you prays the two rakʿahs of Fajr, let him lie on his right side.
Here a qawl, a saying attributed to the Prophet ﷺ, is transmitted: “let him lie down.”