Sunan an-Nasa'i 2346
سنن النسائي#2346SahihIt was narrated that Ibn 'Abbas said:"The Messenger of Allah would fast until we said he would not break his fast, and he would not fast until we said he does not want to fast. And he never fasted any month in full apart from Ramadan, from the time he came to Al-Madinah
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 - Agreed Upon
In-book reference: 22:257