مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3934
Musnad of Abdullah bin Mas'ood
it was narrated from `Abdullah, from the Prophet (ﷺ) that he said: "Every betrayer will have a banner, and it will be said: This is the betrayer of So and so.”
Musnad Ahmad 3959Its isnad is saheeh, al-Bukhari (3186) and Mustim (1736)]