The Messenger of Allah ﷺ forbade a man from lying on his back with one leg crossed over the other.
عن رسول الله ﷺ أنه نهى أن يستلقي الرجل، ويثني إحدى رجليه على الأخرى.
Ibn Hibban (5554) and Tahawi in Sharh Maani al-Athar (4/277) both narrated it through Rawh bin Qasim, from Amr bin Dinar, from Abu Bakr bin Hafs bin Umar bin Saad bin Abu Waqqas, from Abu Hurairah, who said, and then he related it. Its isnad is sahih.