Jami` at-Tirmidhi 797
جامع الترمذي#797Da'ifAmir bin Mas'ud narrated that:The Prophet said: "Fasting during the winter is an easy reward
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Zubair Ali ZaiDaif
In-book reference: 8:116