25 Now his elder son was in the field, and when he came and drew nigh to the house, he heard music and dancing: 26 And he called one of the servants, and asked what these things meant. 27 And he said to him: Thy brother is come, and thy father hath killed the fatted calf, because he hath received him safe. 28 And he was angry, and would not go in. His father therefore coming out began to entreat him.
Ambrose: The younger son, that is the Gentile people, is envied by Israel as the elder brother, the privilege of his father’s blessing.
Augustine: When then the fullness of the Gentiles shall have come in, His father will go out at the fit time that all Israel also may be saved, . . . For there shall be at some time an open calling of the Jews to the salvation of the Gospel. Which manifestation of calling he calls the going out of the father to entreat the elder son.
29 And he answering, said to his father: Behold, for so many years do I serve thee, and I have never transgressed thy commandment, and yet thou hast never given me a kid to make merry with my friends: 30 But as soon as this thy son is come, who hath devoured his substance with harlots, thou hast killed for him the fatted calf.
Augustine: With respect to the commandment not transgressed, it at once occurs, that it was not spoken of every command, but of that most essential one, that is, that he was seen to worship no other God but one, the Creator of all. Nor is that son to be understood to represent all Israelites, but those who have never turned from God to idols.
Jerome: He says, You never gave me a kid, that is, no blood of prophet or priest has delivered us from the Roman power.
Augustine: The harlots are the superstitions of the Gentiles, with whom he wastes his substance, who having left the true marriage of the true God.
Jerome: In that which he says, You have killed for him the fatted calf, he confesses that Christ has come, but envy has no wish to be saved.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. III (London: Rivington, 1843).