Chapter 8: Prayers (Salat)
Narrated 'Aisha: the mother of believers: Allah enjoined the prayer when He enjoined it, it was two rak 'at only (in
every prayer) both when in residence or on journey. Then the prayers offered on journey remained the
same, but (the rak 'at of) the prayers for non-travelers were increased.
Sahih al-Bukhari 350