One place where Orgien's belief in eschatological idealism can be found is in De Principiis, 2.11, where he criticizes those who literally interpret prophecies to mean that resurrected bodies will be like current bodies, the heavenly city will be made of precious stones and metals, and that Christians will rule like earthly kings do now.
On resurrected bodies:
Certain persons, then, refusing the labour of thinking, and adopting a superficial view of the letter of the law, and yielding rather in some measure to the indulgence of their own desires and lusts, being disciples of the letter alone, are of opinion that the fulfilment of the promises of the future are to be looked for in bodily pleasure and luxury; and therefore they especially desire to have again, after the resurrection, such bodily structures as may never be without the power of eating, and drinking, and performing all the functions of flesh and blood, not following the opinion of the Apostle Paul regarding the resurrection of a spiritual body.
[They imagine] to themselves that the earthly city of Jerusalem is to be rebuilt, its foundations laid in precious stones, and its walls constructed of jasper, and its battlements of crystal; that it is to have a wall composed of many precious stones, as jasper, and sapphire, and chalcedony, and emerald, and sardonyx, and onyx, and chrysolite, and chrysoprase, and jacinth, and amethyst.
Then, again, agreeably to the form of things in this life, and according to the gradations of the dignities or ranks in this world, or the greatness of their powers, they think they are to be kings and princes, like those earthly monarchs who now exist.
Summarizing his criticism, he says that these people, "while believing in Christ, understand the divine Scriptures in a sort of Jewish sense, drawing from them nothing worthy of the divine promises."
Instead of this, he argues that we should interpret Scripture "in conformity with the spiritual view of things." Regarding eating by resurrected bodies, he writes:
Those, however, who receive the representations of Scripture according to the understanding of the apostles, entertain the hope that the saints will eat indeed, but that it will be the bread of life.
Gregg R. Allison summarizes Origen's view this way:
Moving beyond a literal interpretation, Origen approached Scripture to find its spiritual meaning. [...] Christians could still hope for the fulfillment of the promises of the future, but the hope was not for physical goods but spiritual blessings. (Historical Theology, 687)