Sahih al-Bukhari 1954
صحيح البخاري#1954SahihNarrated `Umar bin Al-Khattab:Allah's Messenger (ﷺ) said, "When night falls from this side and the day vanishes from this side and the sun sets, then the fasting person should break his fast
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 30:61