Alcuin of York — on Rev 6:14 (COMMENTARY ON REVELATION)

“And the heaven departed as a book folded up. Just as the reprobates fall from the Church not physically but through their transgressions, so does the same Church, in its elect, depart from among the wicked not by a physical departure but by faith and work. Moreover it is right for the Church to be represented by a book, because it contains in itself the commandments for all heavenly life, not only written on parchments with a pen, but also written on the fleshly tablets of the heart by the Spirit of God. Note also that the book is said to be folded up, for just as no one can see what a folded-up book contains except those for whom it is voluntarily opened, so does the Church of the elect, in time of persecution, shut its innermost parts for strangers and discreetly open them inside for its people. And every mountain, and the islands were moved out of their places. By the mountains we should understand men of very high dignity who surpass others in words and virtues, about whom it is said, I have lifted up my eyes to the mountains. [Ps. 120:1] By the islands we understand people of lesser justice who still waver in tribulations. So the fact that mountains and islands are said to have been moved out of their places is related to the above interpretation in which the Church of the saints departs by faith and work from the company of the wicked; for a familiarity with the wicked it was mixed with was a little like its place.”