Musnad Ahmad 1179:3

Abu Mu'awiyah narrated to us, he said: Al-A'mash narrated to us, from Abu Sufyan, from Jabir, from Umm Mubashir, she said: The Messenger of Allah (peace and blessings of Allah be upon him) entered upon me while I was in one of the gardens of Banu al-Najjar, in which there were graves of some of them who had died during the Jahiliyyah (pre-Islamic era). He heard them being punished, so he went out saying: "Seek refuge in Allah from the punishment of the grave." She said: I said: O Messenger of Allah, are they being punished in their graves? He said: "Yes, a punishment that the beasts hear."