Sunan an-Nasa'i 2123
سنن النسائي#2123SahihIt was narrated that Abu Hurairah said:"The Messenger of Allah mentioned the crescent and said: 'When you see it, fast and when you see it, stop fasting, and if it is obscured from you (too cloudy), then count 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: 22:34