Sahih Muslim 1737
Sahih Muslim · Book 32: The Book of Jihad and Expeditions · The prohibition of betrayal
Anas reported Allah's Messenger (ﷺ) having said this:
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى ، وَعُبَيْدُ اللَّهِ بْنُ سَعِيدٍ ، قَالاَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ ، عَنْ شُعْبَةَ ، عَنْ ثَابِتٍ ، عَنْ أَنَسٍ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لِكُلِّ غَادِرٍ لِوَاءٌ يَوْمَ الْقِيَامَةِ يُعْرَفُ بِهِ " .
There would be a flag for every perfidious person on the Day of Judgment by which he will be recognised.