كتاب الصلاة
4  
Prayer
(3a)
Chapter: Observing Prayer Early in the Period - Section 1
(2)
باب تعجيل الصلوات
Mishkat al-Masabih 598
She also said that God’s Messenger would pray the Morning Prayer, and the women would depart wrapped up in their woolen garments, being unrecognizable because of the darkness before dawn. (Bukhari and Muslim)
وَعَنْهَا قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَيُصَلِّي الصُّبْحَ فَتَنْصَرِفُ النِّسَاءُ مُتَلَفِّعَاتٌ بمروطهن مَا يعرفن من الْغَلَس
  مُتَّفَقٌ عَلَيْهِ   (الألباني) حكم   :
Reference : Mishkat al-Masabih 598
In-book reference : Book 4, Hadith 33