The Messenger of Allah ﷺ said, "Do not insult the dead, for you will hurt the living."
قال رسول الله ﷺ: لا تسبوا الأموات، فتؤذوا الأحياء.
Tirmidhi (1982) narrated it, and Ibn Hibban (3022) graded it sahih, through the route of Abu Dawud Hafari. Ahmad (18209) also narrated it through the route of Abu Naeem Fadl bin Dukayn. Both routes go back through Sufyan Thawri, from Ziyad bin Alaqa, who said, "I heard Mughira bin Shuba," and then he mentioned it. Its isnad is sahih.Tirmidhi said, "The companions of Sufyan differed regarding this hadith. Some of them narrated it in the same way as the narration of Hafari, while others narrated it from Sufyan, from Ziyad bin Alaqa, who said, 'I heard a man narrating from Mughira bin Shuba, from the Prophet ﷺ,' similarly."I say, Abu Naeem also narrated it in the same way as the narration of Hafari, and the man who was speaking in front of Mughira bin Shuba was also a companion. So the hadith revolves between the two companions. For more, see the Book of Funerals.