Musnad Ahmad

It is narrated from Hazrat Abu Saeed Khudri (may Allah be pleased with him) that I heard the Prophet (peace and blessings of Allah be upon him) say: When Yajuj and Majuj are released and they will emerge upon the people as Allah Almighty has said, that they will descend from every height, then they will spread over the face of the earth and the Muslims will withdraw into their cities and fortresses. Yajuj and Majuj will seize their livestock and drink up all the water of the earth, so much so that some of them will pass by a river and drink all its water, leaving it dry. Then others from among them will pass by it and say, "There must have been water here once." In short, when there will be no human left on the face of the earth except those who have secured themselves in fortresses or cities, one of them will say, "We have dealt with the people of the earth, now only the people of the sky remain." Saying this, he will shake his spear and throw it towards the sky, and the spear will be returned to them covered in blood as a trial and test for them. Meanwhile, Allah will send a worm like a locust upon their necks, which will appear at their necks, and all of them will die at once, and the next day not a single sound will be heard from them. The Muslims will say among themselves, "Is there anyone who will risk his life to go and see what has become of this enemy?" So a man, with the intention of reward, thinking that he will be killed, will descend from the fortress and see that they are all dead, their corpses lying on top of each other. At that time, he will call out, "O group of Muslims! Glad tidings for you, Allah has sufficed you against your enemy." Thus, the Muslims will come out of their cities and fortresses, and when their animals go out to graze, the flesh of Yajuj and Majuj will be spread everywhere for them to eat, and by eating it, they will become so healthy and fat that they will never have been so healthy from any grass or the like.