Messenger of Allah ﷺ used to offer the Fajr prayer when it was still dark and the believing women used to return (after finishing their prayer) and nobody could recognize them owing to darkness, or they could not recognize one another.  

أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يُصَلِّي الصُّبْحَ بِغَلَسٍ فَيَنْصَرِفْنَ نِسَاءُ الْمُؤْمِنِينَ لاَ يُعْرَفْنَ مِنَ الْغَلَسِ أَوْ لاَ يَعْرِفُ بَعْضُهُنَّ بَعْضًا