Yahya related to me from Malik from Ibn Shihab from a man of the
family of Khalid ibn Asid that he said to Abdullah ibn Umar, "Abu Abd
ar-Rahman, we find the fear prayer and the prayer when settled
mentioned in the Quran, but we do not find any mention of the
travelling prayer in it." Ibn Umar said, "Son of my brother! Allah
the Mighty and Majestic sent us Muhammad, may Allah bless him and
grant him peace, and we know nothing. We only do as we saw him doing."
Muwatta Malik Book 9, Hadith 9