The Book of Prayers (Kitab Al-Salat)

Muslim :: Book 4 : Hadith 884

Salim narrated it from his father ('Abdullah b. Umar) that the Messenger of Allah (may peace be upon him) said: When women ask permission for going to the mosque, do not prevent them.

Source materials are from the University of Southern California MSA site
Hadith eBooks converted from Imaan Star