Sunan an-Nasa'i 2129

سنن النسائي#2129Sahih

Ibn 'Abbas narrated that the Messenger of Allah said:"Fast when you see it, and stop fasting when you see it, and if clouds prevent you from seeing it, then complete the number, and do not fast ahead of Ramadan

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

In-book reference: 22:40