A man of fiqh is asked about a man of hadith and says: Avoid his hadith, for he errs, or narrates what he did not hear, or has no insight into fatwa

Imam al-Shafi'i (may Allah have mercy on him) said: "This is neither enmity nor backbiting, when he says it to someone about whom he fears that he will follow him and fall into error by following him; and this is among the meanings of testimonies."

Sayyiduna Anas (may Allah be pleased with him) said: A funeral was passed by the Prophet (peace and blessings be upon him), and it was praised with good, so the Prophet (peace and blessings be upon him) said: "It has become obligatory." Another funeral was passed by, and it was spoken of badly; he (peace and blessings be upon him) said: "It has become obligatory." Then he (peace and blessings be upon him) was asked: Did you (peace and blessings be upon him) say of both that it has become obligatory? He (peace and blessings be upon him) said: "The believers are Allah's witnesses on the earth."

Ibrahim bin Abd al-Rahman al-Udhri (may Allah have mercy on him) said that the Messenger of Allah (peace and blessings be upon him) said: "This knowledge will be inherited in every generation by its upright ones; they remove from it the interpretations of the ignorant, they reject the false claims of the people of falsehood, and they put an end to the distortions of the extremists."

Ibrahim bin Abd al-Rahman (may Allah have mercy on him) said: Our shaykhs have also narrated it in the same way.

Abdullah bin Utbah (may Allah have mercy on him) said: Subay'ah bint al-Harith (may Allah be pleased with her) gave birth fifteen days after the death of her husband. Abu al-Sanabil (may Allah be pleased with him) passed by her and said: "Do you intend to marry?" She said: "Yes." Abu al-Sanabil (may Allah be pleased with him) said: "First complete the waiting period ('iddah) of four months and ten days." She came to the Prophet (peace and blessings be upon him) and mentioned this, and he (peace and blessings be upon him) said: "Abu al-Sanabil erred. When someone comes to you whom you are pleased with, inform me."
This is a good (hasan) mursal report, and it has supporting reports (shawahid). We have narrated from a group of the Companions and the Successors clarification of the status of one in whom something is found that requires the rejection of his report; this is not the place for it, except that al-Shafi'i (may Allah have mercy on him) brought this issue into the discussion of the testimony of the people of desires, so we have pointed to some of its proofs. And success is from Allah.

Bahz bin Hakim narrates from his father, from his grandfather (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "Do you refrain from mentioning the wicked person?" He said: "Mention his faults, so that people may know him and beware of him."
This hadith is known through al-Jarud bin Yazid al-Naysaburi, and the scholars of hadith rejected it from him. Abu Abdullah Muhammad bin Ya'qub al-Hafiz said more than once: Whenever Abu Bakr al-Jarudi passed by the grave of his grandfather in the cemetery of al-Husayn bin Mu'adh, he would say: "O father, had you not narrated the hadith of Bahz bin Hakim, I would have visited you."
The Shaykh said: A group of weak narrators stole it from him and narrated it from Bahz bin Hakim, and nothing about it is authentic.

Sayyiduna Anas bin Malik (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever casts off the garment of modesty, there is no backbiting regarding him."
This too is not strong, and Allah knows best.