Abdul Hameed bin Ja'far عبد الحميد بن جعفر بن عبد الله · The Book of Fasting

"The Messenger of Allah traveled during Ramadan and fasted until he reached 'Usfan. Then he called for a vessel and drank during the day when the prople could see him, then he did not fast."

"I said to Mujahid: 'What about fasting while traveling?' He said: 'The Messenger of Allah used to fast (sometimes) and not fast (sometimes)."'

he asked the Messenger of Allah about fasting while traveling. He said: "If," then he said something to the effect that: "If you want, then fast, and if you want, then do not fast.