(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
Humaid reported that Anas (Allah be pleased with him) was asked about fasting during Ramadan while travelling. He said:
We travelled with the Messenger of Allah (ﷺ) during the month of Ramadan, but neither the observer of the fast found fault with the breaker of the fast, nor the breaker of the fast found fault with the observer of the fast.
Reference: Sahih Muslim 1118 a
In-book reference: Book 13, Hadith 126
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2482