مُوَطَّأُ مَالِكٍ
Muwatta Malik 325
Prayer in Congregation
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَائِشَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم كَانَتْ تُصَلِّي فِي الدِّرْعِ وَالْخِمَارِ .
Yahya related to me from Malik that he had heard that A'isha, the wife of the Prophet, (ﷺ), used to pray in a shift and head-covering.
Arabic/English book reference: Book 8, Hadith 36