Maliks Muwatta Book 47, Hadith Number 18.
Section : Shunning People.
Yahya related to me from Malik from Muslim ibn Abi Maryam from Abu Salih as-Samman that Abu Hurayra said, “The actions of people are presented twice each week, on Monday and Thursday. Every trusting slave is forgiven except for a slave who has enmity between him and his brother. It is said, ‘Leave these two until they turn in tawba. Leave these two until they turn in tawba.'”