Imam Ali (AS) said, ‘Among the definitions of the custodianship of an Imam whose obedience is obligatory is to know that he is immune from committing mistakes, errors, intentional wrongs, and from all sins, petty and grave. He never makes mistakes or sin, and neither is he ever diverted from the issues that endanger the religion by any sort of diversion. He is the most knowledgeable of all people about what Allah has made lawful and unlawful, His obligations, recommendations and rulings. He stands needless of the entire world whilst they all need him. And he is the most generous and courageous of men.