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. (ID)
English reference (ID): Book 16, Hadith 1547 (ID)
Arabic reference (ID): Book 16, Hadith 1504 (ID)