Musnad Ahmad 32:67

Ibn Abi ‘Adi narrated to us, from Humayd, from Anas, who said: The Prophet, peace and blessings of Allah be upon him, entered one of the gardens of Medina belonging to Banu al-Najjar. He heard a sound from a grave, so he asked about it: "When was this one buried?" They said: "O Messenger of Allah, this one was buried during the Jahiliyyah (pre-Islamic era)." He was amazed by that and said: "Were it not that you would not bury one another, I would have supplicated to Allah to let you hear the punishment of the grave."