Sahih Muslim Book 6, Hadith Number 2481.
Chapter : Permissibility of observing the fast or not observing it in the month of Ramadan for a traveller.
Abu Nadra reported Abu Sa’id al. Khudri and Jabir b. Abdullah as saying: We travelled with the Messenger of Allah (may peace be upon him). The observer of the fast observed it, and the breaker of the fast broke it, but none of them found fault with each other.