(a) Thus, offerings are gifts; that is, they are offered to God without the compulsion of any law, or at least without any determination by law of the amount to be given. Natural reason teaches man that he should bestow something from his goods in this manner as a thank offering for the divine bounty, when there are representatives of God to whom the gift may be given. The gift should be a free-will offering (Exod., xxv, 2), unless there are special circumstances that render it a debt, such as contract, promise, custom, or the need of the ministers of the Church.
(b) They are made immediately to God Himself, and so they differ from tithes or other dues that are paid to the clergy for their support.
(c) They are not changed at all in the act of worship (e.g., an offering of sacred vessels or altar furnishings), or at least they are not changed into the sacred condition of a sacrificial victim (e.g., offerings of candles, incense, etc., that are consumed during Mass). Thus, simple oblation differs from sacrificial oblation.
(d) They are devoted to the service of God, since they are gifts made to Him. Hence, they are used in divine worship and, if consecrated (e.g., chalices, vestments), may not be used for other purposes; or they are used for the needs of the ministers of divine worship or of the poor, since those who serve the altar should live by the altar (I Cor., ix. 14), and Our Lord shared His purse with the poor (Matt., xxvi. 9, 11).
(e) They are given as a mark of honor to God, especially in recognition of favors received from Him. Thus, in the Old Law the people were obliged to give the first-fruits of their fields and crops to God, in thanksgiving for the gift of the promised land and of its fruits (Deut., xxvi. 10).
2184. Goods Unsuitable as Offerings to God.—There are certain goods, however, that should not be used as offerings to God.
(a) Thus, those goods that are forbidden by positive law may not be offered to God. In the Old Law certain animals could not be offered to God, either because they were legally unclean (e.g., dogs were associated with pagan rites and were regarded as symbols of rapacity), or because they were of inferior quality (e.g., a blind or lame sheep or other animal worthless to its owner).
(b) Those goods that the offerer has no right to give away or that are unsuitable on account of circumstances may never be given as offerings to God. Thus, one may not make an offering to God of money that belongs to another (Ecclus., xxxiv. 21); a son may not give as a gift to God the money he should spend on his needy parents (Matt., xv. 3-6). Neither may one offer corrupted wine for the Mass, nor the wages of prostitution to the church if there will be scandal, nor gifts that are mean and contemptible, etc.
2185. Contributions.—Contributions to the support of the clergy and church causes are neither sacrifices nor offerings in the strict sense of these words, since they are given not directly to God but to the ministers of God. The manner of making contributions to the Church has varied with time.
(a) Thus, in the first ages of the Church clerics having the care of souls were supported by the voluntary gifts of the people. These gifts were made especially during Mass. Bread and wine and other things necessary for divine worship and the support of the clergy were brought at the Offertory (the origin of the present Offertory collection), while food for the agapae or for the poor was presented for a blessing towards the end of the Canon, or before Mass.