وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ صَالِحِ بْنِ كَيْسَانَ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ عَائِشَةَ، زَوْجِ النَّبِيِّ صلى الله عليه وسلم أَنَّهَا قَالَتْ فُرِضَتِ الصَّلاَةُ رَكْعَتَيْنِ رَكْعَتَيْنِ فِي الْحَضَرِ وَالسَّفَرِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَزِيدَ فِي صَلاَةِ الْحَضَرِ ‏.‏

Yahya related to me from Malik from Salih ibn Kaysan from Urwaibn az-Zubayr that A'isha, the wife of the Prophet, may Allah blesshim and grant him peace, said, "The prayer was prescribed as tworakas, both when settled and when travelling. Then the travellingprayer was kept as it was, and an increase was made in the prayer whensettled. " Translation Not Available

Book Ref: Muwatta Imam Malik Book 9 Hadith 337
Web Ref:  Muwatta Imam Malik Book 9 Hadith 9