Sunan an-Nasa'i 2359
سنن النسائي#2359SahihIt was narrated from Usamah bin Zaid:That the Messenger of Allah used to fast continually and it ws said that he would not break his fast, and he used not to fast and it was said that he would not fast
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahHasan Sahih
Al-AlbaniHasan Sahih
Zubair Ali ZaiIsnaad Hasan
In-book reference: 22:270