The Prophet ﷺ said, "Every traitor will have a banner on the Day of Resurrection by which he will be recognized."
حدثنا عفان حدثنا شعبة عن ثابت
عن النبي ﷺ قال لكل غادر لواء يوم القيامة يعرف به
Its isnad is sahih. It has already appeared at 13549.