Ambrose of Milan

Let one who still doubts hear the testimony of the Gospel, for the Son of God said, "We have played for you, and you have not danced." The Jews who did not dance and knew not how to clap their hands were abandoned, but the Gentiles were called and applauded God in spirit. "The fool folds his hands together and eats his own flesh," that is, he becomes involved in the concerns of the body and eats his own flesh, just as does all-powerful death. And such a one will not find eternal life. …

Letters 51-60 (Letter to Bishop Sabinus) ↗

Jerome

"The fool folds his hands and eats his own flesh." This is the man that is described as slow to comprehend in Proverbs [Cfr Prov. 19, 24.], holding his chest in his hands. For poverty, although he is a fast runner, catches up with him and he eats his own flesh because of the extent of his hunger, but this is said in exaggeration. He is the sort of man who thinks that having one fist of corn and living idly and in a stupor is better than filling each hand by working. …

Commentary on Ecclesiastes ↗

Bonaventure

"The fool folds" etc. Here thirdly is touched upon the vanity of sloth, on account of which a man is rendered weary and lazy toward every good and thereby foolish. Therefore he says: "The fool folds his hands"; therefore a fool, because lazy; Proverbs chapter twelve: "He who pursues idleness is most foolish"; Proverbs chapter six: "Go to the ant, O sluggard, and learn wisdom." This fool "folds his hands," because he refuses to work; Proverbs chapter twenty-six: "The sluggard hides his hands under his armpit and finds it labor if he …

Commentary on Ecclesiastes, Chapter 4 ↗