2 For actions not done lawfully and piously, are not of advantage, though they may be reputed to be so, but they rather argue hypocrisy in those who venture upon them. Therefore, although such persons feign to offer sacrifices, yet they hear from the Father, 'Your whole burnt-offerings are not acceptable, and your sacrifices do not please Me; and although you bring fine flour, it is vanity, incense also is an abomination unto Me. ' For God does not need anything; and, since nothing is unclean to Him, He is full in regard to them, as He testifies, by Isaiah, saying, 'I am full.'
Now there was a law given about these things, for the instruction of the people, and to prefigure things to come, for Paul says to the Galatians; 'Before faith came, we were kept guarded under the law, being shut up in the faith which should afterwards be revealed unto us; wherefore the law was our instructor in Christ, that we might be justified by faith. ' But the Jews knew not, neither did they understand, therefore they walked in the daytime as in darkness, feeling for, but not touching, the truth we possess, which [was contained] in the law; conforming to the letter, but not submitting to the spirit.
And when Moses was veiled, they looked on him, but turned away their faces from him when he was uncovered. For they knew not what they read, but erroneously substituted one thing for another. The prophet, therefore, cried against them, saying, 'Falsehood and faithlessness have prevailed among them.' The Lord also therefore said concerning them, 'The strange children have dealt falsely with Me; the strange children have waxen old. ' But how gently does He reprove them, saying, 'Had you believed Moses, you would have believed Me, for he wrote of Me.'
But being faithless, they went on to deal falsely with the law, affirming things after their own pleasure, but not understanding the Scripture; and, further, as they had hypocritically made a pretence of the plain text of Scripture, and had confidence in this, He is angry with them, saying by Isaiah, 'Who has required these of your hands?' And by Jeremiah, since they were very bold, he threatens, 'Gather together your whole burnt-offerings with your sacrifices, and eat flesh, for I spoke not unto your fathers, nor commanded them in the day that I brought them out of the land of Egypt, concerning whole burnt-offerings and sacrifices.'
For they did not act as was right, neither was their zeal according to law, but they rather sought their own pleasure in such days, as the prophet accuses them, beating down their bondsmen, and gathering themselves together for strifes and quarrels, and they smote the lowly with the fist, and did all things that tended to their own gratification. For this cause, they continue without a feast until the end, although they make a display now of eating flesh, out of place and out of season.
For, instead of the legally-appointed lamb, they have learned to sacrifice to Baal; instead of the true unleavened bread, 'they collect the wood, and their fathers kindle the fire, and their wives prepare the dough, that they may make cakes to the host of heaven, and pour out libations to strange gods, that they may provoke Me to anger, says the Lord. ' They have the just reward of such devices, since, although they pretend to keep the Passover, yet joy and gladness is taken from their mouth, as says Jeremiah, 'There has been taken away from the cities of Judah, and the streets of Jerusalem, the voice of those who are glad, and the voice of those who rejoice; the voice of the bridegroom, and the voice of the bride. ' Therefore now, 'he who among them sacrifices an ox, is as he who smites a man, and he who sacrifices a lamb is as he who kills a dog, he that offers fine flour, is as [if he offered] swine's blood, he that gives frankincense for a memorial, is as a blasphemer.'
Now these things will never please God, neither thus has the word required of them. But He says, 'These have chosen their own ways; and their abominations are what their soul delights in. '
Source: Letters (New Advent)