Sunan an-Nasa'i 2173
سنن النسائي#2173SahihAbu Hurairah narrated that the Messengre of Allah said:"None should fast one or two days ahead of the month except, someone who had a prior habit for fasting, in which case let him fast
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 ZaiHasan
In-book reference: 22:84