Sunan an-Nasa'i 2222
سنن النسائي#2222SahihIt was narrated from Abu Umamah that he asked the Messenger of Allah:"Which deed is best?" he said: "Take to fasting, for there is nothing equal to it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 22:133