Cutting off the kinship, which means cutting off communication and meeting with relatives, is one of the major sins, and it is not allowed to leave it with bad-tempered or sinful relatives. Qur'an and hadiths forbid severing relations with relatives and emphasize on connecting them.
Quran and Sunnah
In Quran:
May it not be that if you were to wield authority you would cause corruption in the land and ill-treat your blood relations?[1]
Interpretation:
Imam Sadiq (peace be upon him) read this verse and then said:
Would it then be possible for you, if you were to take charge and gain authority and rule, to spread corruption on earth and sever your ties of kinship?
Then he said: This verse was revealed about the children of our uncles; the children of Abbas and the children of the Umayyads”.[2]
Another interpretation:
So, is it expected of you that if you become the ruler of the affairs of the people or become the ruler, that you will cause mischief and destruction in the land due to taking bribes and shedding blood and disobeying the command of God and other things, and by sending them out of pleasure, that is, of course, from You will come that when you aspire to the office of emir and government, you will cause chaos in the land due to arrogance and excessive glory and will cut off mercy as you used to do in the time of ignorance.
Or, it is not far from you to turn away from the religion of Islam and to follow the path of ignorance, which will cause corruption and bloodshed unjustly and cut off mercy and plunder the people of Islam.[3]
Consequences and punishment of Termination of the Kinship:
The Prophet (peace be upon him):
Three groups do not go to heaven; The one who always drinks wine, the one who is always engaged in magic and the one who cut ties with his relatives.[4]
Imam Ali (peace be upon him):
The owner of three traits will never die to see their plague. Oppression, cutting the kinship and swearing falsely to fight against God.[5]
[1] Quran [47–22]: فَهَلْ عَسَيْتُمْ إِنْ تَوَلَّيْتُمْ أَنْ تُفْسِدُوا فِي الْأَرْضِ وَتُقَطِّعُوا أَرْحَامَكُمْ
[2] Bihar al-Anwar, vol. 24, p. 320:
قَرَأَ أَبُو عَبْدِ اللَّهِ (علیه السلام) فَهَلْ عَسَیْتُمْ إِنْ تَوَلَّیْتُمْ وَ سُلِّطْتُمْ وَ مَلَکْتُمْ أَنْ تُفْسِدُوا فِی الْأَرْضِ وَ تُقَطِّعُوا أَرْحامَکُمْ ثُمَّ قَالَ نَزَلَتْ هَذِهِ الْآیَهْ فِی بَنِی‌عَمِّنَا بَنِی‌الْعَبَّاسِ وَ بَنِی‌أُمَیَّهْ
[3] Sharh Usul al-Kafi, Al-Mazandarani, Mullah Salih, vol. 12, p. 31: فقال إني فضلت قريشا على العرب وأتممت عليهم نعمتي وبعثت إليهم رسولي فبدلوا نعمتي كفرا وأحلوا قومهم دار البوار.
[4] Al-Khasal, vol. 1, p. 179: ثَلَاثَهْ لَا یَدْخُلُونَ الْجَنَّة مُدْمِنُ خَمْرٍ وَ مُدْمِنُ سِحْرٍ وَ قَاطِعُ رَحِم
[5] Al-Kafi, vol. 2, p. 347: ثَلَاثُ خِصَالٍ لَا یَمُوتُ صَاحِبُهُنَّ أَبَداً حَتَّی یَرَی وَبَالَهُنَّ الْبَغْیُ وَ قَطِیعَة الرَّحِمِ وَ الْیَمِینُ الْکَاذِبَهْ یُبَارِزُ اللَّهَ بِهَا