Sayyiduna Hamzah bin Amr al-Aslami (may Allah be pleased with him) said: I said to the Messenger of Allah (peace and blessings be upon him): I find myself strong enough to fast on a journey; is there any sin upon me? So the Messenger of Allah (peace and blessings be upon him) said: "It is a concession from Allah, the Blessed and Exalted. Whoever takes it has done well, and whoever prefers to fast, there is no sin upon him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8158