The Messenger of Allah ﷺ would say the Fajr prayer after which the women would depart wrapped up their woolen garments, being unrecognizable because of the darkness before dawn.  

أَنَّهَا قَالَتْ إِنْ كَانَ رَسُولُ اللَّهِ ﷺ لَيُصَلِّي الصُّبْحَ فَيَنْصَرِفُ النِّسَاءُ مُتَلَفِّعَاتٍ بِمُرُوطِهِنَّ مَا يُعْرَفْنَ مِنَ الْغَلَسِ  

Offer Fajr prayer at dawn, for it is most productive of rewards to you or most productive of reward.  

قَالَ رَسُولُ اللَّهِ ﷺ أَصْبِحُوا بِالصُّبْحِ فَإِنَّهُ أَعْظَمُ لأُجُورِكُمْ أَوْ أَعْظَمُ لِلأَجْرِ