Musnad Ahmad 27:1233

Ishaq ibn Isa narrated to us, Layth narrated to me, Ibn Shihab narrated to me, from Abdullah ibn Abi Bakr ibn Abd al-Rahman, from Umayyah ibn Abdullah ibn Khalid ibn Asid, that he said to Abdullah ibn Umar: "We find the prayer of residence and the prayer of fear in the Quran, but we do not find the prayer of travel in the Quran." Ibn Umar said to him: "O son of my brother, Allah, the Almighty and Majestic, sent Muhammad, may Allah bless him and grant him peace, to us while we knew nothing. So we only do as we saw Muhammad do."