Jami` at-Tirmidhi 740
جامع الترمذي#740SahihAbu Hurairah narrated that :the Messenger of Allah said: "The most virtuous fasting after the month of Ramadan is Allah's month Al-Muharram
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
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih Muslim
In-book reference: 8:59