From the early Church Fathers to now.
“The scroll symbolizes the prophets and the apostles. In it the Old Testament was written on the reverse and the New on the obverse. Moreover, the scroll symbolizes the secret, the spiritual teaching—and in such a dignified manner that it may be read on both sides. In reality it is of such a kind that there is a connection between reading the outside and understanding the inside.”
“If God were to stand up as the avenger of sin, the church would lose many of its saints and certainly would be deprived of the apostle Paul.”
“(Verse 9.) In which was a wrapped book, and he unfolded it before me, and it was written inside and outside: and there were written in it lamentations, and a song, and woe. And he said to me: Son of man, whatever you find, eat. Concerning the wrapped book, the seventy chapters of the book were translated. In the hand of the Lord sitting on the throne, which was sent and extended. Concerning which it is also said in the Psalms: In the chapter of the book it is written about me (Psalm 39:8). Chapter, let us understand the beginning. This book was wrapped and sealed, written inside and outside, or before and after, of such difficulty that no one was able to open and read it, neither in heaven, nor on earth, nor underneath the earth, except the lion of the tribe of Judah, the root of David and Jesse, whom John in the Apocalypse said devoured it (Rev. 5), not whole, but in a chapter, that is, in the beginning. For it is impossible for human nature to devour the entire treasure of this book. And He unfolded it before the prophet, and He made it available to be read and understood, who is said to be marked in Isaiah as belonging to the people who do not believe (Isa. XXIX). For even to this day the veil is placed upon the Jews in the old Testament. And it was written before and after; concerning things to come and concerning things past. Truly, outwardly in historical writing, but inwardly in spiritual understanding, of which the Psalmist says: The glory of the king's daughter is from within (Psal. XLIV, 14). And there were written in it both inward and outward lamentations, and song, and woe. Lamentations, concerning those who are called to penance, just as Samuel and the Apostle Paul mourned and lamented for Saul and the Corinthians, whom they desired to save (2 Chronicles 16; 2 Corinthians 12). Song about those who are worthy of God's testimony, and whom the Psalmist commands: Sing to the Lord a new song (Psalm 95 and 97, verse 1). Furthermore, woe to those who have completely despaired and, when they come into the depths of sin, they scorn (Prov. XVIII).”
“"And I looked, and behold, a hand was sent to me, in which was a rolled-up book; and he spread it out before me, and it was written inside and outside." Just as the order of preachers is designated by the prophet, so the pages of Sacred Scripture are designated by the book which he received. Now the scroll is the obscure speech of Sacred Scripture, which is wrapped up in the profundity of its meanings, so that it may not easily be penetrated by the understanding of all. But the scroll is unrolled before the prophet, because the obscurity of sacred speech is opened before preachers. The hand of God had extended a rolled-up scroll when He was saying to the apostles: "The kingdom of heaven has become like a man who sowed good seed in his field. But while men were sleeping, his enemy came and sowed weeds among the wheat, and went away. And when the grass had grown and produced fruit, then the weeds also appeared," and the rest which your charity remembers even without my recounting it. But He unrolled the scroll which He had shown rolled up when He explained what He had spoken through riddles, saying: "He who sows the good seed is the Son of Man. The field is the world. The good seed, these are the sons of the kingdom; but the weeds are the sons of wickedness. The enemy who sowed them is the devil. The harvest is the consummation of the age, and the harvesters are angels. Therefore just as the weeds are gathered and burned with fire, so it will be at the consummation of the age." And so the rolled-up scroll is unrolled when what had been set forth obscurely is opened through the breadth of understanding. Truth unrolled this rolled-up scroll when He accomplished in His disciples what is written: "Then He opened their minds to understand the Scriptures."”
“Concerning this book it is further added: "Which was written within and without." For the book of sacred eloquence is written within through allegory, without through history. Within through spiritual understanding, but without through the simple sense of the letter, still suited to those who are weak. Within, because it promises invisible things; without, because it arranges visible things through the rectitude of its precepts. Within, because it promises heavenly things, but without because it teaches how earthly things are to be despised, whether they are to be used or fled from out of desire. For it speaks certain things concerning heavenly secrets, but commands other things in external actions. And indeed those things which it commands outwardly are plain, but those things which it narrates concerning internal matters cannot be fully apprehended.”
“Whence it is written: "Stretching out the heaven like a skin, who covers its upper parts in the waters." For what is signified by the name of heaven except sacred Scripture? From which the sun of wisdom, and the moon of knowledge, and from the ancient Fathers the stars of examples and virtues shine for us. This is stretched out like a skin, because, formed through the tongue of flesh by its writers, it is unfolded before our eyes by being expounded through the words of teachers. But what is signified by the name of waters except the most holy choirs of angels? Of which it is written: "And let the waters that are above the heavens praise the name of the Lord." The Lord covers the upper parts of this heaven in the waters, because the deep things of sacred eloquence, that is, those things which it narrates concerning the nature of divinity or concerning eternal joys, while we are still ignorant, are known to the angels alone in secret. Therefore this heaven is both stretched out before us, and yet its upper parts are covered in the waters, because both certain things of sacred eloquence now lie open to us through the opening of the spirit, and certain things which can be manifest to the angels alone are still kept hidden from us. Concerning which hidden things, however, we already perceive a part through spiritual understanding, we have already received the pledge of the Holy Spirit, because we have not yet fully known these things, and yet we love them from the depths of our heart, and in many spiritual senses which we have already known, we are fed with the food of truth.”
“Let him therefore say: "Which was written within and without," because in sacred eloquence the strong are satisfied by more hidden and sublime sayings, and we little ones are nourished by plainer precepts. Whence it is written: "The high mountains are for the deer, the rock is a refuge for the hedgehogs." For let those have the mountains of understanding who already know how to make the leaps of contemplation. But let the rock be a refuge for the hedgehogs, because we little ones, covered with the thorns of our sins, even if we cannot understand lofty things, are saved in the refuge of our rock, that is, in faith in Christ. Whence also it is said to certain ones: "I judged myself to know nothing among you except Christ Jesus, and him crucified." As if he were saying: Because I considered that you could not grasp the mysteries of his divinity, I spoke to you only of the weakness of his humanity.”
The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.