It was narrated from 'Aishah that Hamzah bin 'Amr Al-Aslami asked the Messenger of Allah:"O Messenger of Allah, I am a man who fasts continually: shoud I fast when traveling?" He said: "Fast if you wish and break you fast if you wish." 'Ata said: "someone who heard him told me that Ibn 'Umar (said) that the Prophet said: 'Whoever fasts every day of his life, and then he has not fasted

English translation · Sunan an-Nasa'i