Sahih al-Bukhari 3186
صحيح البخاري#3186SahihNarrated Anas:The Prophet (ﷺ) said, ''Every betrayer will have a flag on the Day of Resurrection" One of the two subnarrators said that the flag would be fixed, and the other said that it would be shown on the Day of Resurrection, so that the betrayer might be recognized by it
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: 58:28