It is recommended for a man to wear his best and most perfect clothes when praying, and there is nothing more perfect than the clothes that he adorns himself with in the company of people, such as that which covers his body, and he wears an ʿamāmah and upper garment. It has been mentioned from Ibn ʿUmar, may Allah be pleased with him, that he saw his servant Nāfiʿ praying bareheaded, so he said to him, ‘If you were to go out into the presence of people, do you think you would go out like this?’ He replied, ‘No’. He said, ‘Then Allah is more deserving of being adorned for.’ This has been related by Abū Dāwūd and others.
It is recommended for a woman to pray in three garments: a khimār that covers her head and neck, a chemise (dirʿ) that covers her body and feet and thick milḥafah–and a milḥafah is a jilbāb–due to what has been related from ʿUmar, may Allah be pleased with him, in which he said, ‘A woman prays in three garments: a chemise, a khimār and a lower garment (izār).’ It is also on the authority of ʿAbdullah ibn ʿUmar, may Allah be pleased with both of them, who said, ‘A woman prays in a chemise, a khimār and a milḥafah.’ Imam ash-Shāfiʿī said, ‘People in general have agreed on the chemise and the khimār, and whatever is added to that is better and more concealing.’
[Translated from Ghāyat al-Munā by Sheikh Muḥammad Bā ʿAṭiyyah (Amman: Dār al-Fatḥ, 1429/2008), p.271]