Sahih al-Bukhari 3188
صحيح البخاري#3188SahihNarrated Ibn `Umar:The Prophet (ﷺ) said, "Every betrayer will have a flag which will be fixed on the Day of Resurrection, and the flag's prominence will be made in order to show the betrayal he committed
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: 58:29