Sunan an-Nasa'i 2420
سنن النسائي#2420SahihIt was narrated from Jarir bin 'Abdullah that the Prophet said:"Fasting three days of each month is fasting for a lifetime, and the shining days of Al-Bid, the thirteenth, fourteenth and fifteenth
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahHasan
Al-AlbaniHasan
Zubair Ali ZaiSahih
In-book reference: 22:331