Sahih Bukhari
Good Manners and Form (Al-Adab)
Volume: 008 / Book Number: 073 / Hadith Number: 197
Narrated Ibn 'Umar:
Allah's Apostle 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."