Muwatta Malik, Book 8, Hadith 38 (USC-MSA) ⓘ

Yahya related to me from Malik from a reliable source from Bukayr ibn Abdullah ibn al-Ashajj from Busr ibn Said that when Ubaydullah ibn al-Aswad al-Khawlani was in the room of Maimuna, the wife of the Prophet, may Allah bless him and grant him peace, she used to pray in a shift and head-covering, without a waist-wrapper.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ الثِّقَةِ، عِنْدَهُ عَنْ بُكَيْرِ بْنِ عَبْدِ اللَّهِ بْنِ الأَشَجِّ، عَنْ بُسْرِ بْنِ سَعِيدٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ الأَسْوَدِ الْخَوْلاَنِيِّ، وَكَانَ، فِي حَجْرِ مَيْمُونَةَ زَوْجِ النَّبِيِّ صلى الله عليه وسلم أَنَّ مَيْمُونَةَ كَانَتْ تُصَلِّي فِي الدِّرْعِ وَالْخِمَارِ لَيْسَ عَلَيْهَا إِزَارٌ ‏.‏