Sahih Muslim
The Book of Virtue, Good Manners and Joining of the Ties of Relationship (Kitab Al-Birr was-Salat-I-wal-Adab)
Book Number: 032 / Hadith Number: 6206
Anas b. Malik reported Allah's Messenger (may peace be upon him) as saying: Neither nurse mutual hatred, nor jealousy, nor enmity, and become as fellow. brothers and servants of Allah. It is not lawful fora Muslim that he should keep his relations estranged with his brother beyond three days.