1 The oblation of the Church, therefore, which the Lord gave instructions to be offered throughout all the world, is accounted with God a pure sacrifice, and is acceptable to Him; not that He stands in need of a sacrifice from us, but that he who offers is himself glorified in what he does offer, if his gift be accepted. For by the gift both honour and affection are shown forth towards the King; and the Lord, wishing us to offer it in all simplicity and innocence, did express Himself thus: “Therefore, when you offer your gift upon the altar, and shall remember that your brother has ought against you, leave your gift before the altar, and go your way; first be reconciled to your brother, and then return and offer your gift.” We are bound, therefore, to offer to God the first-fruits of His creation, as Moses also says, “You shall not appear in the presence of the Lord your God empty;” so that man, being accounted as grateful, by those things in which he has shown his gratitude, may receive that honour which flows from Him.
Source: Adversus haereses (New Advent)