To what extent is the saying of one of the Salaf authentic: "Were I to see one of my brothers with wine dripping from his beard, I would say perhaps it was spilled on him, and were I to find him standing on a mountain saying: 'I am your Lord Most High,' I would say he is reciting the verse"?

The two aforementioned sayings have no basis and were not uttered by any of the Salaf (pious predecessors) or Khalaf (later generations). The fundamental principle is to have a good opinion of Muslims and the prohibition of having a bad opinion of them without clear evidence. It is authentically reported from Umar ibn Al-Khattab, may Allah be pleased with him, that he said: "Place your brother's matter on its best interpretation, until something comes to you from him that overwhelms you." The Holy Quran warned against excessive suspicion and considered some of it a sin. The Prophet, peace and blessings be upon him, also forbade suspicion because it is the most untruthful of speech. Therefore, having a bad opinion is not permissible except when there are clear reasons necessitating suspicion, such as someone known for فسق (immorality) and a clear corroborating sign is found with them. As for someone known for their piety and righteousness, having a good opinion of them is obligatory, and having a bad opinion of them is forbidden.