Musnad Ahmad 1060:42

Yahya narrated to us, from Shu'bah, 'Awn ibn Abi Juhayfah narrated to me, from his father, from al-Bara', from Abu Ayyub: That the Prophet, peace and blessings of Allah be upon him, went out after the sun had set, and he heard a sound. He said: "The Jews are being punished in their graves."