Sahih Muslim 1927
صحيح مسلم#1927SahihAbu Basra Ghifari reported:The Messenger of Allah (ﷺ) led us in the 'Asr prayer at (the place known as) Mukhammas, and then said: This prayer was presented to those gone before you, but they lost it, and he who guards it has two rewards in store for him. And no prayer is valid after till the onlooker appears (by onlooker is meant the evening star)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 6:355