Musannaf Ibn Abi Shayba 3:5165

Abu Bakr narrated to us, Zayd ibn al-Hubab narrated to us, Ja'far ibn Ibrahim—from the descendants of Dhu al-Janahayn—narrated to us, he said: Ali ibn Umar narrated to me, from his father, from Ali ibn al-Husayn, that he saw a man coming to a gap that was at the grave of the Prophet, may God bless him and grant him peace, so he would enter into it and supplicate. So he called him and said: "Shall I not narrate to you a hadith I heard from my father, from my grandfather, from the Messenger of God, may God bless him and grant him peace? He said: 'Do not take my grave as a festival, and do not take your houses as graves. And send blessings upon me, for your blessings reach me wherever you are.'"