Sa'd bin Abi Waqas told us that: The Messenger of Allah SAW said: "Fighting a Muslim is Kufr and defaming him is evildoing".
The Prophet Muhammad [SAW] was very clear on this point; he said that fighting a Muslim is an act of disbelief and defaming him is evildoing. This means that we should never resort to violence when dealing with our fellow believers; instead, we should use dialogue and understanding in order to resolve any disputes between us peacefully. We must also remember not to speak ill about other Muslims; doing so would be considered an evil deed according to the teachings of Islam.