From Sahih Bukhari (Hadith 6178):
Narrated Ibn `Umar:Allah's Messenger (ﷺ) said, "A flag will be fixed on the Day of Resurrection for every betrayer, and it will be announced (publicly in front of everybody), 'This is the betrayal (perfidy) so-and-so, the son of so-and-so
Reference: Bukhari 6178