It is narrated from Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "It is not permissible for any Muslim to sever relations with his (Muslim) brother for more than three days. Whoever severs relations for more than three days and dies in that state, he will enter Hell." Its chain is authentic. Narrated by Ahmad and Abu Dawood.