Irenaeus of Lyons, Against Heresies 4.18
The Church's offering, which the Lord commanded to be offered throughout the world, is regarded as a pure sacrifice before God and is accepted by Him; God does not need a sacrifice from us, but the one who offers is glorified in the very act of offering, provided his gift is accepted.
Gifts presented to a king demonstrate honor and affection, and the Lord, desiring us to offer in all simplicity and innocence, taught this when He said: when you bring your gift to the altar and remember that your brother has something against you, leave your gift there before the altar, go first and be reconciled to your brother, and then return to offer your gift (Matthew 5:23-24).
We must therefore offer God the firstfruits of His creation, just as Moses also says: you shall not appear empty-handed before the presence of the Lord your God (Deuteronomy 16:16); thus the person who shows gratitude in these things is deemed worthy, and the one who comes from God receives honor.
It is not the kind of offerings that is rejected, for there were offerings then and there are offerings now: sacrifices among the people of old, sacrifices also in the Church; but the form has changed, since now the offering is made not by slaves but by free people.
There is one and the same Lord, yet the character of a slave's offering is distinct from that of a free person's, so that through our offerings the sign of freedom is displayed.
Nothing with Him is idle, without a sign, or without meaning; for this reason those of old had their tithes consecrated, but those who have received freedom set aside what is theirs for the Lord's purposes, giving cheerfully and freely not lesser things but rather with hope of greater things, like that widow and this poor person who cast their entire livelihood into the treasury of God.
From the beginning God looked with favor on Abel's gifts, because he offered with simplicity and justice, but He did not look on Cain's sacrifice, for he harbored zeal and malice against his brother and division in his heart; God, exposing his hidden thoughts, said: 'Have you not sinned, if you offer correctly but do not divide correctly? Be still; for God is not pleased by sacrifice.'
Latin
Ierrur Ecclesiz oblatio, quam Dominus doeuit offerri in universo mundo, purum sacrificium reputatum est apud Deum, et acceptum est ei: non quod indigeat a nobis sacrificium, sed quoniam is qui offert, glorificatur ipse in eo quod offert, si acceptetur munus ejus. Per musus enim erga regem, et honos, et affectio ostenditur: quod in omni simplicitate et innocentia Dominus volens nos offerre, preedicavit dicens: Cwm igitur offers munus tuum ad altare, et recordatus fueris, quoniam frater twus habet aliquid adversum te, dimitte munus tuum ante altare, et vade primum reconciliari fratri tuo, et tune reversus offeres munus tuum. Offerre igitur oportet Deo primitias ejus creature, sicut et Moyses ait: Non apparebis vacuus ante conspectum Domini Dei tui ; ut in gratus exstitit homo, in his gratus eis deputatus, eum qui est ab eo percipiat honorem. Et non genus oblationum reprobatum est; oblationes enim et illic, oblationes autem et hic: sacrificia in populo, sacrificia et in Ecclesia : sed species immutata est tantum, quippe cum jam non a servis, sed a liberis offeratur. Unus enim et idem Dominus; proprium autem character servilis oblationis, et proprium liberorum, uti et per oblationes ostendatur indicium libertatis. Nihil enim otiosum, nec sine signo, neque sine argumento apud eum. Et propter hoc illi quidem decimas suorum habebant consecratas: qui autem perceperunt libertatem, quee sunt ipsorum ad dominicos éecernunt usus, hilariter et libere dantes ea, non que sunt minora, utpote majorum spem habentes vidua illa et paupere hic totum victum suum mittente in gazophylacium Dei. 2. Ab initio enim respexit Deus ad munera Abel, quoniam cum simplicitate et justitia offerebat; super sacrificium autem Cain non respexit, quoniam cum zelo et malitia, que erat adversus fratrem, divisionem habebat in corde, quemadmodum occulta ejus arguens Deus ait: Nonne si recte offeras, recte autem non dividas, peccasti? ' quiesce: quoniam non sacrificio placatur Deus.