The choice between fasting and not fasting when travelling — Sahih Muslim 1122 a

We set out during the month of Ramadan with the Messenger of Allah (ﷺ) in such an intense heat that one of us would place his hand over his head (in order to protect himself) against the excessive heat, and none among us was observing the fast, except the Messenger of Allah (ﷺ) and 'Abdullah b. Rawaha.