مُوَطَّأُ مَالِكٍ
Muwatta Malik 340
Shortening the Prayer
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، عَنْ أَبِيهِ، أَنَّهُ رَكِبَ إِلَى رِيمٍ فَقَصَرَ الصَّلاَةَ فِي مَسِيرِهِ ذَلِكَ . قَالَ مَالِكٌ وَذَلِكَ نَحْوٌ مِنْ أَرْبَعَةِ بُرُدٍ .
Yahya related to me from Malik from Ibn Shihab from Salim ibn Abdullah that his father rode to Rim and shortened the prayer on the journey. Malik said, "That was about four mail-stages." (approximately forty-eight miles).
Arabic/English book reference: Book 9, Hadith 12