"Come here, my nephew, and I will tell you. The Prophet ﷺ only forbade sitting on graves for the purpose of relieving oneself by defecation or urination."
هلم يا ابن أخي أخبرك، إنما نهى النبي ﷺ عن الجلوس على القبور لحدث غائط أو بول.
No references are available.
Tahawi narrated it in Sharh Maani al-Athar (2877), from Sulayman bin Shuayb, who said, Khasib told us, who said, Amr bin Ali told us, who said, Uthman bin Hakeem told us, from Abu Umama, that Zayd bin Thabit said, then he related it.Hafiz said in Fath al-Bari (3/224), "Its narrators are trustworthy."I say, its isnad is hasan because of Khasib, who is Ibn Nasih Harithi. Abu Zura said, "There is no harm in him, Allah willing."Bukhari said, in the chapter on Funerals, the chapter on placing palm branches on the grave, Uthman bin Hakeem said, "Kharija took me by the hand and sat me down on a grave, and told me, on the authority of his uncle Yazid bin Thabit, who said, 'He only disliked that for someone who relieved himself on it.'"Nafi said, "Ibn Umar used to sit on graves."Kharija bin Zayd said, "I remember when we were young men in the time of Uthman, and the most vigorous of us in leaping was the one who would jump onto the grave of Uthman bin Mazun."Bukhari mentioned all of these, and these reports contradict the marfu hadith. So we say, either it did not reach them, or they interpreted the marfu hadith differently, just as Imam Malik and others did.