The Messenger of Allah (ﷺ) as saying: If anyone is on a journey and Ramadan comes... He then narrated the rest of the tradition to the same effect.
Sunan Abi Dawud Book 14, Hadith 99
← Previous Hadith The Messenger of Allah (ﷺ) said: If anyone has a riding beast which carries him to where he can get sufficient food, he should keep the fast of Ramadan wherever he is when it comes.

Sunan Abi Dawud Book 14, Hadith 98 Next Hadith → Ja'far ibn Jubayr said: I accompanied AbuBusrah al-Ghifari, a Companion of the Messenger of Allah (ﷺ), in a boat proceeding from al-Fustat (Cairo) during Ramadan. He was lifted (to the boat), then his meal was brought to him. The narrator Ja'far said in his version: He did not go beyond the houses (of the city) but he called for the dining sheet. He said (to me): Come near. I said: Do you not see the houses? AbuBusrah said: Do you detest the sunnah (practice) of the Messenger of Allah (ﷺ)? The narrator Ja'far said in his version: He then ate (it).

Sunan Abi Dawud Book 14, Hadith 100