Umm al-Mu’minin Sayyida Aisha (may Allah be pleased with her) said: The Messenger of Allah (peace and blessings be upon him) said: “Do not speak ill of the dead, for they have received the recompense of what they did.”
(Commentary on Hadith 2546) From this hadith, it is understood that one should not speak ill of those Muslims who have passed away. To speak badly of them after their death, to mention their faults, is to cause harm to their loved ones, whereas in the hadith of the Messenger of Allah sallallahu alayhi wa sallam, the command is: «الْمُسْلِمُمَنْسَلِمَالْمُسْلِمُونَمِنْلِسَانِهِوَيَدِهِ» meaning, "A Muslim is the one from whose tongue and hand his Muslim brother is safe." This hadith is coming ahead at number (2751).