Sahih Bukhari Volume 002, Book 013, Hadith Number 023.
Narated By Ibn Umar : One of the wives of Umar (bin Al-Khattab) used to offer the Fajr and the 'Isha' prayer in congregation in the Mosque. She was asked why she had come out for the prayer as she knew that Umar disliked it, and he has great ghaira (self-respect). She replied, "What prevents him from stopping me from this act?" The other replied, "The statement of Allah's Apostle (p.b.u.h) : 'Do not stop Allah's women-slave from going to Allah s Mosques' prevents him."