Musnad Abu Ya'la al-Mawsili 2:102

Abu Khaythama narrated to us, Waki' narrated to us, Sufyan narrated to us, from Zubayd, from 'Abd al-Rahman ibn Abi Layla, from 'Umar, who said: The prayer of travel is two rak'ahs, the prayer of Fitr is two rak'ahs, the prayer of Adha is two rak'ahs, and the prayer of Jumu'ah is two rak'ahs. [They are] complete, not shortened, upon the tongue of your Prophet, may Allah bless him and grant him peace.