“The Messenger of Allah (ﷺ) said that Ya’jooj and Ma’jooj are digging every day until they can almost see sunlight, then the one who is in charge of them says, “Go back, we will dig again tomorrow.”
Then Allah restores (the barrier) and makes it stronger than it was. (This will continue) until the appointed time. When Allaah wishes to send them against the people, they will dig until they can almost see sunlight, then the one who is in charge of them will say, “Go back, we will dig again tomorrow, in sha Allah.”
This time he will say “in sha Allah”, so when they come back (the next day), they will find it as they left it, so they will dig their way out and emerge to attack the people.
They will dry up water (by drinking it, because of their great numbers), and the people will seek to protect themselves from them in their fortresses. They will fire their arrows into the sky, and the arrows will come back down covered in blood (as a test for them), and they will say, “We have defeated the people of the earth and have gained the upper hand over the people of heaven.”
Then Allah will send worms on the napes of their necks, which will kill them. The Messenger of Allah (peace and blessings of Allah be upon him) said: “By the One in Whose hand is my soul, the beasts of the earth will grow fat from their flesh.”
Sunan Ibn Majah 4080