Abdullah ibn Tawus, from his father, from Ibn Abbas, who said: We were sitting with the Prophet (PBUH) when Ali ibn Abi Talib (AS) entered and said, "Peace be upon you, O Messenger of God." He replied, "And upon you be peace, O Commander of the Faithful." And he said: "God has ordained this title, and it is not permissible for anyone to be called by this name whom God Most High has not named with it." (Mi'at Manqaba, vol. 1, p. 51)
The Messenger of God (PBUH) named Ali (AS) "Commander of the Faithful" and said: This title is from God, and no one has the right to use this title wrongly or apply it to others.
Muhammad ibn Ziyad, from al-Mufaddal ibn Umar, from Ja'far ibn Muhammad, from his father, from Ali ibn al-Husayn, from his father, from the Commander of the Faithful, Ali (AS): He was sitting in the Rahba with the people around him when a man stood up and said to him, "O Commander of the Faithful, you are in the station in which God has placed you—yet your father is being tormented in the Fire!" He said to him, "Silence! May God smash your mouth! By Him who sent Muhammad in truth as a prophet, were my father to intercede for every sinner on the face of the earth, God Most High would accept his intercession. Is my father tormented in the Fire, while I, his son, am the apportioner of Paradise and the Fire?" (Mi'at Manqaba, vol. 1, p. 174)
The narrator says: The Commander of the Faithful (AS) was sitting in the wide open square before the mosque of Kufa, with the people gathered in a circle around him, when, without cause, a man spoke insolently and said: O Commander of the Faithful! You hold such an exalted station, yet your father is tormented in the Fire. The Commander of the Faithful (AS) rebuked him: Be silent! May God stop your mouth with clay! By the God who raised Muhammad to prophethood, if my father were to intercede for all the sinners of the earth, God would accept it of him. Can the father be tormented in the Fire while his son is the apportioner of the Fire and Paradise?!