الكافي 2/1/75/7

7. Ali ibn Ibrahim has narrated from his father from Ibn Abi ‘Umayr from Mansur ibn Yunus from abu al-Mamun al-Harithi who has said the following: “Once I asked Abu ‘Abdillah عليه السلام ‘What are the rights of the believer on the believer?’ The Imam said, ‘Of the rights of the believer on the believer is to have compassion for him in his heart, assist him with his property, protect his interests in his absence in the matters of his family and support him against those who do injustice to him. If a benefit is distributed among the Muslims in his absence his believing brother should secure his share thereof. When he dies, he should visit his gravesite, must not do injustice to him, must not deceive him, must not violate his trust, must not betray him, must not call him a liar, must not say to him, ‘Fie upon you.’ If he says fie up on you then no guardianship ( Walayah ) relations will remain between them. If he says, ‘You are my enemy,’ one of them becomes an unbeliever and if he accuses him, belief in his heart will melt as salt melts in water.’”