Hamzah bin 'Amro Al-Aslami (RAA) narrated, 'I said to the Messenger of Allah (ﷺ) 'O Messenger of Allah (ﷺ)! I find within me the strength to fast while traveling. Would there be any blame upon me if I were to do so?' The Messenger of Allah (ﷺ) said to him, "It is a concession from Allah. Whoever takes it has done well. Whoever likes to fast, there is no blame upon him."Related by Muslim.
English reference: Book 5, Hadith 695
Arabic reference: Book 5, Hadith 673