And when ye ask of them (the wives of the Prophet) anything, ask it of them from behind a curtain. That is purer for your hearts and for their hearts. And it is not for you to cause annoyance to the messenger of Allah, nor that ye should ever marry his wives after him. Lo! that in Allah’s sight would be an enormity. (Quran, 33:53)
O Prophet! Tell thy wives and thy daughters and the women of the believers to draw their cloaks close round them (when they go abroad). That will be better, so that they may be recognised and not annoyed. Allah is ever Forgiving, Merciful. (Quran, 33:59)