It is narrated from Sayyiduna Hisham bin ‘Amir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: It is not lawful for any Muslim to abandon his brother for more than three nights; if they exceed three, then as long as they persist in severing relations, they will remain deviated from the truth. And whoever among them returns first, his return will be an expiation for his sins. So if he greets (with salam) but the other does not reply and rejects his greeting, then the angels will reply to him and the other’s reply will be given by Satan. If such two people die while persisting in their severance, they will never be gathered together in Paradise. In another narration: They will never enter Paradise.