Musnad Ahmad 5:670

'Affan narrated to us, Hammad ibn Salamah narrated to us, 'Ali ibn Zayd informed us, from Rabi'ah ibn al-Nabighah, from his father, from 'Ali, who said: "The Messenger of Allah (may Allah bless him and grant him peace) forbade the visiting of graves." He then mentioned its meaning, except that he said: "And beware of every intoxicant."