A'ishah (RAA) narrated that the Messenger of Allah (ﷺ) said:
"Avoid reviling the dead, they have already seen the result of (the deeds) that they forwarded before them." Related by Al-Bukhari. (IT)
English reference (IT): Book 16, Hadith 1547 (IT)
Arabic reference (IT): Book 16, Hadith 1504 (IT)