Mukhtasar Bukhari

Narrated from Ummul Momineen Aisha Siddiqa (may Allah be pleased with her), the wife of the Prophet (peace be upon him), that Hamza bin Amr Aslami (may Allah be pleased with him) asked the Prophet (peace be upon him): "Should I fast while traveling?" And he used to fast frequently. So the Prophet (peace be upon him) said: "If you wish, then fast, and if you wish, then do not fast."