Sunan an-Nasa'i 2119
سنن النسائي#2119SahihIt was narrated from Abu Hurairah that the Messenger of allah sadi:"When you see the crescent then fast, and when you crescent then fast, and when you see it, stop fasting. If it is obscured from you (too cloudy), then fast thirty days
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 Muslim
In-book reference: 22:30