(15) باب جواز الصوم والفطر في شهر رمضان للمسافر في غير معصية إذا كان سفره مرحلتين فأكثر وأن الأفضل لمن أطاقه بلا ضرر أن يصوم ولمن يشق عليه أن يفطر
A hadlth like this has been transmitted on the authority of Ibn Shibab who said that they (the Compnions of the Holy Prophet) followed the latest of his commands and looked upon it as one abrogating (the previous ones) and the most firm.
Reference: Sahih Muslim 1113 d
In-book reference: Book 13, Hadith 113
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2469