Irenaeus — on Rev 20:11 (Against Heresies Book V)

“And in the Apocalypse John saw this new [Jerusalem] descending upon the new earth. For after the times of the kingdom, he says, "I saw a great white throne, and Him who sat upon it, from whose face the earth fled away, and the heavens; and there was no more place for them." And he sets forth, too, the things connected with the general resurrection and the judgment, mentioning "the dead, great and small." "The sea," he says, "gave up the dead which it had in it, and death and hell delivered up the dead that they contained; and the books were opened. Moreover," he says, "the book of life was opened, and the dead were judged out of those things that were written in the books, according to their works; and death and hell were sent into the lake of fire, the second death." Now this is what is called Gehenna, which the Lord styled eternal fire. "And if any one," it is said, "was not found written in the book of life, he was sent into the lake of fire."”