Sunan an Nasai
2256
Sahih Lighairihi+2

It was narrated that Saeed bin Al-Musayyab said:"The Messenger of Allah said: 'It is not righteousness to fast when traveling."' (Sahih) Abu 'Abdur-Rahman (An-Nasai) said: This is a mistake, and what is correct is the one that is before it. We do not know of anyone who followed up Ibn Kathir

Sahih LighairihiAbu Ghuddah
SahihAl-Albani