The prayer was prescribed two Rak´ak each

 202. Aishah narrated: ´´When the prayers were first enjoined, it was two Rak´ak each. Then this format is approved for travellers and to be performed complete by residents.´´

Az-Zuhri said: I asked ´Urwah: ´What made ´Aishah pray the full prayers (in journey).´´ He replied, ´´She interpreted the matter herself as ´Uthman did.´´