Musnad Abu Ya'la al-Mawsili 160:41

Ahmad ibn al-Miqdam narrated to us, Mu'tamir ibn Sulayman narrated to us, he said: I heard my father narrating from Qatadah, that Abu Rafi' narrated from Abu Hurayrah, from the Messenger of Allah (may Allah bless him and grant him peace), who said: "They dig every day until they are about to see the rays of the sun, then they say: 'We will return to it tomorrow.' So they return to it, and it is as firm as it was before. Then, when their time is reached and Allah (Mighty and Majestic is He) intends to send them upon the people, they say: 'We will return to it tomorrow, if Allah wills.' So they return to it in the state they left it, and they dig it," or as he said. He said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Then the people will flee from them into their fortresses," or as he said. He said: Mu'tamir said: My father said from Qatadah: "They will shoot arrows into the sky, and they will return to them with blood on them, so they will say: 'We have overcome those on earth and conquered the inhabitants of the sky,'" or as he said. He said: "Then Allah will send upon them the *naghaf* (larvae) in their napes, and they will kill them." The Messenger of Allah (may Allah bless him and grant him peace) said: "Until their beasts of burden grow fat and become healthy from eating their flesh," or as he said.