Sahih Muslim Book - 1, Hadith - 217

و حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ حَدَّثَنَا عَبْدُ الصَّمَدِ بْنُ عَبْدِ الْوَارِثِ حَدَّثَنَا أَبِي حَدَّثَنَا حُسَيْنٌ الْمُعَلِّمُ عَنْ ابْنِ بُرَيْدَةَ عَنْ يَحْيَى بْنِ يَعْمَرَ أَنَّ أَبَا الْأَسْوَدِ حَدَّثَهُ عَنْ أَبِي ذَرٍّ أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ لَيْسَ مِنْ رَجُلٍ ادَّعَى لِغَيْرِ أَبِيهِ وَهُوَ يَعْلَمُهُ إِلَّا كَفَرَ، وَمَنْ ادَّعَى مَا لَيْسَ لَهُ فَلَيْسَ مِنَّا وَلْيَتَبَوَّأْ مَقْعَدَهُ مِنْ النَّارِ، وَمَنْ دَعَا رَجُلًا بِالْكُفْرِ أَوْ قَالَ عَدُوَّ اللَّهِ! وَلَيْسَ كَذَلِكَ إِلَّا حَارَ عَلَيْهِ.

It was narrated from Abu Dharr that he heard the Messenger of Allah (s.a.w.) say: "Any man who knowingly attributes himself to someone other than his father is guilty of disbelief. Whoever claims something that does not belong to him is not one of us; let him take his place in Hell. Whoever calls a man a disbeliever (Kafir) or says to him: 'O enemy of Allah!' when he is not like that, it will rebound upon him.''