Musnad Ahmad 941:32

Abu Sa’id, the freed slave of Banu Hashim, narrated to us, Qays ibn al-Rabi’ narrated to us, Jami’ ibn Shaddad narrated to us, from Kulthum al-Khuza’i, from Usama ibn Zayd, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said to me: "Bring my companions in to me." So they entered upon him, and he uncovered the veil. Then he said: "May Allah curse the Jews and the Christians; they took the graves of their prophets as places of worship."