Musnad Abu Ya'la al-Mawsili 3:209

Abu Bakr ibn Abi Shaybah 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 us, 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 Allah bless him and grant him peace, so he would enter into it and supplicate. So he forbade him and said: "Shall I not narrate to you a hadith I heard from my father, from my grandfather, from the Messenger of Allah, may Allah bless him and grant him peace? He said: 'Do not take my grave as a festival, and do not take your houses as graves, for your salutations reach me wherever you are.'"