Sahih al-Bukhari, Volume 8, Book 74, Hadith 302 (USC-MSA) ⓘ
Narrated the uncle of `Abbas bin Tamim: I saw Allah's Messenger lying on his back in the mosque and putting one of his legs over the other.
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُفْيَانُ، حَدَّثَنَا الزُّهْرِيُّ، قَالَ أَخْبَرَنِي عَبَّادُ بْنُ تَمِيمٍ، عَنْ عَمِّهِ، قَالَ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فِي الْمَسْجِدِ مُسْتَلْقِيًا، وَاضِعًا إِحْدَى رِجْلَيْهِ عَلَى الأُخْرَى.
also referenced under: Book 79, Hadith 59 (In-Book) & Hadith 6287 (DarusSalam)