Muwatta Imam Malik Book of Shortening the Prayer, Hadith 90
Yahya related to me from Malik from Ibn Shihab from Abbad ibn Tamim from his paternal uncle that he saw the Messenger of Allah ﷺ lying down in the mosque with one foot on top of the other.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ عَبَّادِ بْنِ تَمِيمٍ، عَنْ عَمِّهِ، أَنَّهُ رَأَى رَسُولَ اللَّهِ ﷺ مُسْتَلْقِيًا فِي الْمَسْجِدِ وَاضِعًا إِحْدَى رِجْلَيْهِ عَلَى الأُخْرَى .