3 And again, when He points out that it was not for this that He led them out of Egypt, that they might offer sacrifice to Him, but that, forgetting the idolatry of the Egyptians, they should be able to hear the voice of the Lord, which was to them salvation and glory, He declares by this same Jeremiah: “Thus says the Lord; Collect together your 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 Egypt, concerning burnt-offerings or sacrifices: but this word I commanded them, saying, Hear My voice, and I will be your God, and you shall be My people; and walk in all My ways whatsoever I have commanded you, that it may be well with you.
But they obeyed not, nor hearkened; but walked in the imaginations of their own evil heart, and went backwards, and not forwards.” And again, when He declares by the same man, “But let him that glories, glory in this, to understand and know that I am the Lord, who does exercise loving-kindness, and righteousness, and judgment in the earth;” He adds, “For in these things I delight, says the Lord,” but not in sacrifices, nor in holocausts, nor in oblations. For the people did not receive these precepts as of primary importance (principaliter), but as secondary, and for the reason already alleged, as Isaiah again says: “You have not [brought to] Me the sheep of your holocaust, nor in your sacrifices have you glorified Me: you have not served Me in sacrifices, nor in [the matter of] frankincense have you done anything laboriously; neither have you bought for Me incense with money, nor have I desired the fat of your sacrifices; but you have stood before Me in your sins and in your iniquities.” He says, therefore, “Upon this man will I look, even upon him that is humble, and meek, and who trembles at My words.” “For the fat and the fat flesh shall not take away from you your unrighteousness.” “This is the fast which I have chosen, says the Lord. Loose every band of wickedness, dissolve the connections of violent agreements, give rest to those that are shaken, and cancel every unjust document. Deal your bread to the hungry willingly, and lead into your house the roofless stranger. If you have seen the naked, cover him, and you shall not despise those of your own flesh and blood (domesticos seminis tui). Then shall your morning light break forth, and your health shall spring forth more speedily; and righteousness shall go before you, and the glory of the Lord shall surround you: and while you are yet speaking, I will say, Behold, here I am.” And Zechariah also, among the twelve prophets, pointing out to the people the will of God, says: “These things does the Lord Omnipotent declare: Execute true judgment, and show mercy and compassion each one to his brother. And oppress not the widow, and the orphan, and the proselyte, and the poor; and let none imagine evil against your brother in his heart.” And again, he says: “These are the words which you shall utter. Speak the truth every man to his neighbour, and execute peaceful judgment in your gates, and let none of you imagine evil in his heart against his brother, and you shall not love false swearing: for all these things I hate, says the Lord Almighty.” Moreover, David also says in like manner: “What man is there who desires life, and would fain see good days? Keep your tongue from evil, and your lips that they speak no guile. Shun evil, and do good: seek peace, and pursue it.”
Source: Adversus haereses (New Advent)