Abu Saeed Khudri reported,

We used to travel with the Messenger of Allah ﷺ, and some of us were fasting while others were not. The one not fasting found no fault with the one fasting, and the one fasting found no fault with the one not fasting. They held the view that whoever found within himself the strength to fast, it was good for him to fast, and whoever found himself weak and broke his fast, that too was good.

Tirmidhi 713

Sahih

حدثنا نصر بن علي حدثنا يزيد بن زريع حدثنا الجريري ح قال و حدثنا سفيان بن وكيع حدثنا عبد الأعلى عن الجريري عن أبي نضرة

عن أبي سعيد قال

كنا نسافر مع رسول الله ﷺ فمنا الصائم ومنا المفطر فلا يجد المفطر على الصائم ولا الصائم على المفطر فكانوا يرون أنه من وجد قوة فصام فحسن ومن وجد ضعفا فأفطر فحسن

الترمذي 713صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami Tirmidhi
Book
Fasting
Chapter
Concession for fasting while traveling
Numbering
Darussalam 713
Tirmidhi 713