‘A’isha said that the prayer was prescribed as consisting of two rak'as, and after Allah's Messenger ﷺ emigrated it was prescribed as four, but prayer while travelling was left according to the original prescription. Zuhri said he asked ‘Urwa why ‘A’isha said prayers in the complete form and he replied that she interpreted the matter herself as ‘Uthman did. (Bukhari and Muslim.)