Musnad Abu Ya'la al-Mawsili 42:378

Zuhayr narrated to us, Ya'qub ibn Ibrahim narrated to us, my father narrated to us, from Ibn Ishaq, 'Asim ibn 'Umar ibn Qatadah al-Ansari, then al-Zafari, narrated to me, from Mahmud ibn Labid, one of the Banu 'Abd al-Ashhal, from Abu Sa'id al-Khudri, who said: I heard the Messenger of Allah (ﷺ) saying: "Gog and Magog will be released upon the people, as Allah said: 'And they, from every elevation, will descend' (Al-Anbiya'). They will overwhelm the people, and the Muslims will withdraw from them to their cities and their fortresses, and they will gather their livestock with them. They will drink the waters of the earth, to the extent that some of them will pass by a river and drink what is in it until they leave it dry, such that those who come after them will pass by that river and say: 'There was water here once.' Until, when no one remains of the people except one in a fortress or a city, their speaker will say: 'These are the people of the earth; we have finished with them. There remain the people of the heaven.' Then one of them will shake his spear and throw it toward the heaven, and it will return to him stained with blood, as a trial and a tribulation. While they are in that state, Allah will send worms in their necks, like the larvae of locusts that emerge in their necks, and they will wake up dead, with no sound heard from them. The Muslims will say: 'Is there a man who will sell his soul for us and see what these enemies have done?' A man among them will volunteer for that, seeking reward for his soul, having resigned himself to the fact that he will be killed. He will find them dead, some upon others. He will call out: 'O assembly of Muslims, rejoice! For Allah has sufficed you against your enemy.' So they will emerge from their cities and their fortresses and release their livestock, and they will have no pasture except their flesh, and they will grow fat as the best they have ever grown from any vegetation they have ever encountered."