Cyprian

Isaiah [prophesied] that the Jews would not understand the holy Scriptures, but that they would become intelligible in the last times, after Christ had come: "And all these words shall be to you as the words of a book that is sealed, which, if you shall give to a man that knows letters to read, he shall say, I cannot read, for it is sealed.… But in that day the deaf shall hear the words of the book, and they who are in darkness and in a cloud; the eyes of the blind shall see."

Treatise XII. Three Books of Testimonies Against the Jews 1:4 ↗

Jerome

And the vision of all will be like the words of a sealed book, which when they give to one who knows letters, they will say: read this, and he will answer, I cannot, for it is sealed. And a book will be given to one who knows not letters, and it shall be said to him, read; and he shall answer, I know not letters. …

Commentary on Isaiah ↗

Thomas Aquinas

Third, he sets out the effect of the blinding, for they will not understand the book of the Sacred Scriptures and the visions of all the prophets: and the vision of all shall be unto you as the words of a book that is sealed: and I saw, in the right hand of him that sat on the throne, a book, sealed with seven seals (Rev 5:1).

Commentary on Isaiah ↗

Bonaventure

Sacred Scripture is compared to the water of the sea on account of the profundity of its mysteries. The sea is deep, nor can a man wade across it: so great is the profundity of the mysteries of sacred Scripture that, however illuminated a man may be and however great his industry, he cannot attain to their depth. Hence Isaiah says: "The vision of all things shall be to you as the words of a sealed book, which when they give to one who knows letters, they will say: Read this; and he will answer: I cannot, for it is sealed. …

Collationes de Septem Donis, Collation 4 ↗