Chapter: 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
Authentic
hadith of Sahih Muslim
Sahih Muslim 1117
سَافَرْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَيَصُومُ الصَّائِمُ وَيُفْطِرُ الْمُفْطِرُ فَلاَ يَعِيبُ بَعْضُهُمْ عَلَى بَعْضٍ .
Abu Nadra reported Abu Sa'id al. Khudri and Jabir b. Abdullah as saying:
We travelled with the Messenger of Allah (ﷺ). The observer of the fast observed it, and the breaker of the fast broke it, but none of them found fault with each other.
‘Ā'ishah (may Allah be pleased with her) reported: Hamzah ibn ‘Amr al-Aslami asked the Prophet (may Allah's peace and blessings be upon him): "Should I fast while traveling?" - and he used to fast often - He answered: "If you wish then fast, and if you wish then do not fast."