The Messenger of Allah ﷺ said: "Indeed the one who betrays will have a banner erected for him on the Day of Judgement." [He said:] There are narrations on this topic from 'Ali, 'Abdullah bin Mas'ud, Abu Sa'eed Al-Khudri, and Anas.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ إِنَّ الْغَادِرَ يُنْصَبُ لَهُ لِوَاءٌ يَوْمَ الْقِيَامَةِ قَالَ وَفِي الْبَابِ عَنْ عَلِيٍّ وَعَبْدِ اللَّهِ بْنِ مَسْعُودٍ وَأَبِي سَعِيدٍ الْخُدْرِيِّ وَأَنَسٍ