Revelation 10:10

"I took the book from the hand of the angel, and ate it up." To take the book and eat it up, is, when exhibition of a thing is made to one, to commit it to memory.

"And it was in my mouth as sweet as honey." To be sweet in the mouth is the reward of the preaching of the speaker, and is most pleasant to the hearers; but it is most bitter both to those that announce it, and to those that persevere in its commandments through suffering.

“Our belly stuck to the ground.” They mean that “our belly” consented to the impious persuasion of that dust [i.e., godless persecutors]; for that is what the expression “stuck to” implies.… To cling to God is to do his will. It makes sense, then, to say of the belly that it clung to the earth, when we mean those people who could not hold out under persecution but yielded to the will of the wicked; for this is how they “stuck to the earth.” But why are they called “the belly”? Because they are carnal. It suggests that the church’s mouth is to be found in the saints, in spiritual people, and the church’s belly in the carnal. This is why the church’s mouth is plainly visible, but its belly is covered up, as befits something weaker and more vulnerable. Scripture supports this interpretation in the passage where someone says he was given a book to eat, “and the book was sweet in my mouth but bitter in my stomach.” What can that mean? Surely that the highest precepts, which spiritual persons accept, are unacceptable to the carnal, and that commands that delight the spiritual only give the carnal indigestion. What is in that book, brothers and sisters? “Go and sell all you possess, and give the money to the poor.” How sweet is that command in the church’s mouth! All the spiritual have obeyed it. But if you tell any sensual person to do that, he or she is more likely to walk sadly away, as the rich man in the Gospel walked away from the Lord, than to fulfill the injunction. Why does a carnal person walk away? Because that book, so sweet to the mouth, is bitter in the belly.

“It will be sweet in your mouth but bitter in your stomach.” By the mouth we are to understand the good and spiritual Christians, while by the stomach we understand the carnal and dissolute. And so it is that when the word of God is preached, it is sweet to the spiritual, but to the carnal, whose “god is the belly” as the apostle says, it seems bitter and harsh.

And having eaten, he found them sweet to the mouth, but bitter to the stomach after consumption; for such is every sin. It is sweet in its operation, but bitter in its outcome. For it becomes the cause of punishment, and also, through repentance, it embitters those who have committed it. Such was also the tree forbidden by God in Paradise, which all interpret as leading to sin, producing knowledge of both good and evil (Gen. 2-3); sweet indeed in taste, but evil after experience.

[I told the angel to give me the book.] The church is moved by divine inspiration to be thoroughly instructed about this mystery. “And he said, ‘Take and eat it.’ ” This means that he was to store [the book] in his secret inward parts. “And it will be bitter to your stomach but sweet as honey in your mouth.” This means that when you receive it, you will be delighted by the sweetness of the divine speech and by the hope of the promised salvation and by the sweetness of the divine justice; however, you will then sense bitterness when you begin to preach this to the pious and to the impious. For when the preaching of the divine judgment is heard, some are turned by the bitterness of penance and are changed for the better, while others are offended and become yet more hardened and bear a bitter hatred toward the preachers. “Reprove a wise man, and he will love you; refute a foolish man, and he will hate you.” But the preacher takes in bitterness from either of these two persons. For he either sheds tears with the penitents out of a feeling of compassion, or he is tormented by the bitterness that comes from their failure. For this reason the apostle said, “I have great sorrow and unceasing anguish in my heart; for I wished that I myself were accursed from Christ for the sake of my brothers.” But I think it more apt that the bitterness mentioned here be attributed to the impious alone and the sweetness to the pious. For the spiritual person can say, “How sweet are your words to my taste, sweeter than honey and the honeycomb to my mouth!”

He says that although the knowledge of future things will be sweet to you, at the same time it will be bitter to your stomach, that is, to your heart, which is the dwelling place of spiritual foods. For you will have compassion on those who receive punishments given according to God’s judgment.

And it will make your belly bitter, etc. When you receive it, you will be delighted by the sweetness of the divine word, but you will feel bitterness when you begin to preach and act upon what you have understood. Or indeed, it should be understood according to Ezekiel, who, when he said he had devoured the book, added, And I went in bitterness in the indignation of my spirit.

And I took the book from the hand of the angel, and ate it up: and it was in my mouth, sweet as honey: and when I had eaten it, my belly was bitter. It is right for the mouth, out of which preaching emanates, to represent those who meditate on God's law day and night and say with the Psalmist, How sweet are thy words to my palate! [Ps. 118:103] On the other hand, it is right for the belly, out of which excrements come, to represent fleshly people devoted to earthly pleasures, about whom the elect say, Our belly cleaveth to the earth. [Ps. 43:25] Therefore it is as if food came down through the mouth into the belly, when knowledge of the Scriptures comes through the Church's preachers even to those who live in a fleshly manner. This is why the book, which is sweet in the mouth, becomes bitter in the belly; for what can be more bitter to them than what the Lord commands, Thou shalt not covet thy neighbour's wife, nor anything that is his? [Deut. 5:21] Alternatively, the book is sweet in the mouth when eternal joys are promised in it to readers, like The just shall shine as the sun; [Matt. 13:43] but in the belly, that is in the secret of the mind, it is bitter, since one is confronted in it with strict commandments, like Unless you become as this little child, you shall not enter into the kingdom of heaven. [Variant of Matt. 18:3]