Sahih Bukhari
Shortening the Prayers (At-Taqseer)
Volume: 002 / Book Number: 020 / Hadith Number: 194
Narrated Abu Huraira:
The Prophet (p.b.u.h) said, "It is not permissible for a woman who believes in Allah and the Last Day to travel for one day and night except with a Mahram."