Sunan an Nasai
2303
Sahih+2

It was narrated from Hamzah bin 'Amr that he said to the Messenger of Allah:"I feel able to fast while traveling; is there any sin on me?" He said: "It is a concession from Allah, the mighty and sublime, so whoever accepts it has done well, and whoever wants to fast, there is no sin on him

SahihAbu Ghuddah
SahihAl-Albani