Prohibition of Abusing the Deceased without a valid Legal reason approved by Shari'ah Riyad as-Salihin 1564
Arabic hadith text
وعن عائشة رضي الله عنها قالت: قال رسول الله صلى الله عليه وسلم : "لا تسبوا الأموات فإنهم قد أفضوا إلى ما قدموا". ((رواه البخاري)).
Translation
'Aishah (May Allah be pleased with her) said
The Messenger of Allah (ﷺ) said, "Do not abuse the dead, because they have attained that which they had forwarded (i.e., their deeds, good or bad)."[Al-Bukhari].