1446 - Abu 'Abd Allah narrated to us, he said: 'Abd al-Razzaq narrated to us, he said: Ma'mar narrated to us, from Abu Ishaq, from 'Umar ibn Sa'd, he said: Sa'd ibn Abi Waqqas narrated to us, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Fighting a Muslim is disbelief (kufr), and reviling him is immorality (fusuq), and it is not lawful for a Muslim to abandon his brother for more than three days."