Sayyiduna Abu Khirash Salami (may Allah be pleased with him) narrated from the Prophet (peace and blessings of Allah be upon him), he said: "To abandon a believer for a year is equivalent to killing him." In the gathering were also Muhammad bin Munkadir and Abdullah bin Abi 'Atab; both of them said that we have also heard from them in the same way.
Hadith Referenceالادب المفرد / كتاب / 405
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«صحيح : أخرجه المزي فى تهذيب الكمال : 488/5 - انظر الحديث السابق»
Explanation & Benefits
Shaykh Maulana Usman Muneeb
Benefits and Issues: The point is that just as killing is a major sin (kabirah), similarly, severing speech with a Muslim brother is also a major sin (kabirah), which should not be considered insignificant. Just as the one who kills is punished in every case, likewise, the one who severs relations also becomes deserving of punishment.
Source: Fadlullah al-Ahad: Urdu Commentary on al-Adab al-Mufrad, Page: 405