I heard Messenger of Allah ﷺ say in the company of his Companions: I would be on the Cistern waiting for those who would be coming to me from amongst you. By Allah, some persons would be prevented from coming to me, and I would say: My Lord, they are my followers and people of my Umma. And He would say,: You don't know what they did after you; they had been constantly turning back on their heels (from their religion).  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ وَهُوَ بَيْنَ ظَهْرَانَىْ أَصْحَابِهِ إِنِّي عَلَى الْحَوْضِ أَنْتَظِرُ مَنْ يَرِدُ عَلَىَّ مِنْكُمْ فَوَاللَّهِ لَيُقْتَطَعَنَّ دُونِي رِجَالٌ فَلأَقُولَنَّ أَىْ رَبِّ مِنِّي وَمِنْ أُمَّتِي فَيَقُولُ إِنَّكَ لاَ تَدْرِي مَا عَمِلُوا بَعْدَكَ مَا زَالُوا يَرْجِعُونَ عَلَى أَعْقَابِهِمْ