Augustine of Hippo
Catena Aurea · Lukasevangelium 15
And he said, A certain man had two sons: And the younger of them said to his father, Father, give me the portion of goods that falleth to me. And he divided unto them his living. And not many days after the younger son gathered all together, and took his journey into a far country, and there wasted his substance with riotous living. And when he had spent all, there arose a mighty famine in that land; and he began to be in want. And he went and joined himself to a citizen of that country; and he sent him into his fields to feed swine. And he would fain have filled his belly with the husks that the swine did eat: and no man gave unto him.
(de Quæst. Ev. lib. ii. qu. 33.) But that which is said to have taken place not many days after, namely, that gathering all together he set out abroad into a far country, which is forgetfulness of God, signifies that not long after the institution of the human race, the soul of man chose of its free will to take with it a certain power of its nature, and to desert Him by whom it was created, trusting in its own strength, which it wastes the more rapidly as it has abandoned Him who gave it. Hence it follows, And there wasted his substance in riotous living. But he calls a riotous or prodigal life one that loves to spend and lavish itself with outward show, while exhausting itself within, since every one follows those things which pass on to something else, and forsakes Him who is closest to himself. As it follows, And when he had spent all, there arose a great famine in that land. The famine is the want of the word of truth.