Al-Adab Al-Mufrad 403

Abu Hurayra reported that the Messenger of Allah, may Allah bless
him and grant him peace, said, "Do not hate one another nor contend with
one another. Slaves of Allah, be brothers."

Hisham ibn 'Amir al-Ansari, the cousin of Anas ibn Malik whose
father was killed in the Battle of Uhud, that he heard the Messenger of
Allah, may Allah bless him and grant him peace, say, "It is not lawful
for a Muslim to snub another Muslim for more than three nights. As long
as they are cut off from each other, they are turning away from the Truth.
The first of them to return to a proper state has his expiation for that
inasmuch as he was the first to return to a proper state. If they die while
they are cut off from each other, neither of them will ever enter the Garden.
If one of them greets the other and he refuses to return the greeting or
accept his greeting, then an angel returns the greeting to him and Shaytan
answers the other."

Abu Ayyub, the Companion of the Messenger of Allah, may Allah bless
him and grant him peace, said, "It is not lawful for anyone to cut himself
off from his Muslim brother for more than three nights so that when they
meet, one of them turns his face away in avoidance and the other one turns
his face away as well. The better of them is the one who initiates the
greeting."