(21) باب فِي مَنْعِ الاِسْتِلْقَاءِ عَلَى الظَّهْرِ وَوَضْعِ إِحْدَى الرِّجْلَيْنِ عَلَى الأُخْرَى .
Jalbir b. Abdullah reported Allah's Messenger (ﷺ) as saying:
None of you should lie on his back and place one of his feet upon the other.
Reference: Sahih Muslim 2099 e
In-book reference: Book 37, Hadith 118
USC-MSA web (English) reference(deprecated numbering scheme): Book 24, Hadith 5238