Silsilah as-Sahihah 2383 — Seriousness of breaking relations

Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "If two men enter into Islam and then sever relations with each other, then one of them (i.e., the one who wrongs) goes out of Islam until he gives up severing relations."