Sahih Bukhari | Volume 5 | Hadith Number 576

Narrated by Tawus
Ibn Abbas said, "Allah's Apostle travelled in the month of Ramadan and he fasted till he reached (a place called) 'Usfan, then he asked for a tumbler of water and drank it by the

daytime so that the people might see him. He broke his fast till he reached Mecca." Ibn Abbas used to say, "Allah's Apostle fasted and sometimes did not fast while travelling, so one may fast or may not (on journeys)"