Abu Hurayra reported that the Messenger of Allah, may Allah bless
him and grant him peace, said, "Do not hate one another and do not envy
one another. Let the slaves of Allah be brothers."
Hisham ibn 'Amir 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 one
another, neither of them will ever enter the Garden."
Abu Hurayra reported that the Prophet, may Allah bless him and
grant him peace, said, "You will find that the worst of people in the sight
of Allah on the Day of Rising will be the two-faced person who presents
one face to a group of people and another face to a different group of
people."
Abu Ayyub al-Ansari reported that the Messenger of Allah, may Allah
bless him and grant him peace, said, "It is not lawful for a Muslim to
refuse to speak to his (Muslim) brother for more than three days so that
when they meet, one goes this way and the goes that way. The better of
the two is the one who initiates the greeting."