The Messenger of Allah ﷺ forbade insulting the dead.
حدثنا سفيان عن زياد بن علاقة
نهى رسول الله ﷺ عن سب الأموات
No references are available.
Its chain of transmission is sahih. It is found in Bukhari 2/258, no. 1392, Fath al-Bari, in the Book of Funerals, chapter on the prohibition of reviling the dead, Tirmidhi 4/353, no. 1982, in the Book of Righteousness, chapter on what has been said about reviling, Nasai 33/8, no. 4775, in the Book of Qasamah, chapter on retaliation for a slap, and Darimi 2/311, no. 2511, in the Book of Military Expeditions, chapter on the prohibition of reviling the dead.