Jabir bin Abdullah reported,

The Messenger of Allah ﷺ was on a journey when he saw a crowd gathered around a man who was being shaded. He asked, "What is this?"They replied, "He is fasting."He said, "It is not righteousness to fast while traveling."

Azami 4607

Sahih

عن جابر بن عبد الله، قال

كان رسول الله ﷺ في سفر، فرأى زحاما ورجلا قد ظلل عليه، فقال: ما هذا؟ فقالوا: صائم. فقال: ليس من البر الصوم في السفر.

الأعظمي 4607صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Fasting
Chapter
What is permitted and what is not permitted for the fasting person
Section
Breaking the fast is better for one whom fasting is difficult
Numbering
Jami al-Kamil 4607 (2nd edition)