Ubaidullah bin 'Umar al-Qawariri عبيد الله بن عمر القواريري · The Book of Fasting

"Hamzah said to the Messenger of Allah: 'O Messenger of Allah, should I fast while traveling?' He used to fast a great deal. The Messenger of Allah said to him: "If you wish then fast and if you wish then do not fast."'