صَحِيحُ مُسْلِمٍ
Sahih Muslim 1118 a
كتاب الصيام
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
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا أَبُو خَيْثَمَةَ، عَنْ حُمَيْدٍ، قَالَ سُئِلَ أَنَسٌ - رضى الله عنه - عَنْ صَوْمِ رَمَضَانَ فِي السَّفَرِ فَقَالَ سَافَرْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي رَمَضَانَ فَلَمْ يَعِبِ الصَّائِمُ عَلَى الْمُفْطِرِ وَلاَ الْمُفْطِرُ عَلَى الصَّائِمِ .
Sahih Muslim, 1118 aSahihصحيح