حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ رَجُلٍ، مِنْ آلِ خَالِدِ بْنِ أَسِيدٍ أَنَّهُ سَأَلَ عَبْدَ اللَّهِ بْنَ عُمَرَ فَقَالَ يَا أَبَا عَبْدِ الرَّحْمَنِ إِنَّا نَجِدُ صَلاَةَ الْخَوْفِ وَصَلاَةَ الْحَضَرِ فِي الْقُرْآنِ وَلاَ نَجِدُ صَلاَةَ السَّفَرِ فَقَالَ ابْنُ عُمَرَ يَا ابْنَ أَخِي إِنَّ اللَّهَ عَزَّ وَجَلَّ بَعَثَ إِلَيْنَا مُحَمَّدًا صلى الله عليه وسلم وَلاَ نَعْلَمُ شَيْئًا فَإِنَّمَا نَفْعَلُ كَمَا رَأَيْنَاهُ يَفْعَلُ ‏.‏

Yahya related to me from Malik from Ibn Shihab from a man of thefamily of Khalid ibn Asid that he said to Abdullah ibn Umar, "Abu Abdar-Rahman, we find the fear prayer and the prayer when settledmentioned in the Qur'an, but we do not find any mention of thetravelling prayer in it." Ibn Umar said, "Son of my brother! Allahthe Mighty and Majestic sent us Muhammad, may Allah bless him andgrant him peace, and we know nothing. We only do as we saw him doing." Translation Not Available

Book Ref: Muwatta Imam Malik Book 9 Hadith 336
Web Ref:  Muwatta Imam Malik Book 9 Hadith 8