It is not permissible to
put any type of animal dung in a graveyard or over graves, as it constitutes an insult to the dead people buried there. It is authentically reported that the Prophet (peace be upon him)
Forbade the plastering of graves, sitting on them, and building over them.
who said that this is a Hassan Sahih [good authentic] Hadith) It is also authentically reported that the Prophet (peace be upon him) said,
“Do not sit on graves or offer Salah (Prayer) towards them.”
Therefore, if sitting on graves is forbidden, whether or not it is accompanied by urination or defecation, then putting dung on them is also forbidden. This is insulting to the dead; also because the inviolability of a Muslim after death is the same as it is during lifetime. (Part No. 8; Page No. 443) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.