Hadith 372
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، أَنَّ أَبَاهُ، كَانَ يُصَلِّي فِي الصَّحْرَاءِ إِلَى غَيْرِ سُتْرَةٍ .
Yahya related to me from Malik from Hisham ibn Urwa that his father used to pray in the desert without a sutra
Mauquf Sahih (Salim al-Hilali)
Muwatta Malik 372 · Book 9, Hadith 47