This is a weak chain of transmission.

The fourth is from Ibn ʿAbbas, attributed to the Prophet, with similar wording. Al-Tabarani reported it in al-Awsat with a weak chain of transmission.

1992 — “Backbiting is to mention of a person what he dislikes to hear.”

Malik reported it in al-Muwaṭṭaʾ (3/150, Halabi edition) from al-Walid ibn ʿAbdullah Sayyad, who related that al-Muttalib ibn ʿAbd al-Malik ibn Hantab al-Makhzumi informed him: “A man asked the Messenger of Allah, peace and blessings be upon him, ‘What is backbiting?’ The Messenger of Allah, peace and blessings be upon him, replied, ‘That you mention …’ He asked, ‘O Messenger of Allah, even if it is true?’ The Messenger of Allah, peace and blessings be upon him, replied, ‘If you say something false, then that is slander.’” Ibn al-Mubarak also reported it in al-Zuhd (704), from Malik, with similar wording.

I say: This is a mursal chain of transmission. Concerning this al-Muttalib, al-Hafiz said in al-Taʿjil: “He frequently transmitted mursal reports, and his hearing from Abu Hurayrah has not been established. Perhaps he took it from ʿAbd al-Rahman ibn Yaʿqub.”

Al-Hafiz included a biographical notice on al-Walid from which it is understood that no one besides Malik narrated from him, and that Ibn Hibban mentioned him in the third tier of al-Thiqat. Al-Suyuti stated in the introduction to Isʿaf al-Muwaṭṭaʾ bi-Rijal al-Muwaṭṭaʾ that all of Malik’s shaykhs are reliable. Thus, it is a mursal report with an authentic chain of transmission. It is corroborated by the hadith of Abu Hurayrah, attributed to the Prophet, with the same meaning; I have traced it in Ghayat al-Maram fi Takhrij al-Halal wa-al-Haram (426).

Al-Suyuti also cited the hadith in Zawaʾid al-Jamiʿ, as narrated by al-Kharaʾiti in Masawi al-Akhlaq, from al-Muttalib ibn ʿAbdullah ibn Hantab, attributed to the Prophet, with the wording: “with what he has by way of khilfah,” with an fāʾ—that is, behind his back and without his knowledge.