صَحِيحُ مُسْلِمٍ
Sahih Muslim 1113 c
The Book of Fasting
It is permissible to fast or not to fast during Ramadan for one who is travelling for no sinful purpose, if his journey is two stages or further. But it is better for the one who is able to fast without suffering any harm to do so, and the one for whom it is difficult may break the fast
حَدَّثَنِي مُحَمَّدُ بْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، بِهَذَا الإِسْنَادِ قَالَ الزُّهْرِيُّ وَكَانَ الْفِطْرُ آخِرَ الأَمْرَيْنِ وَإِنَّمَا يُؤْخَذُ مِنْ أَمْرِ رَسُولِ اللَّهِ صلى الله عليه وسلم بِالآخِرِ فَالآخِرِ . قَالَ الزُّهْرِيُّ فَصَبَّحَ رَسُولُ اللَّهِ صلى الله عليه وسلم مَكَّةَ لِثَلاَثَ عَشْرَةَ لَيْلَةً خَلَتْ مِنْ رَمَضَانَ .
It has been narrated on the authority of Zuhri with the same chain of transmitters that breaking of fast (in a journey) is the final of the two commands (whether one may fast or one may break it), and it is the last command of the Messenger of Allah (ﷺ) which is to be accepted as final. Zuhri said: The Messenger of Allah (ﷺ) marched on Mecca on the morning of 14th of Ramadan (lit. when thirteen nights had passed).
Sahih Muslim, 1113 cSahihصحيح