Objection 2: Further, in the same passage it is forbidden to offer "the price of a dog" in the house of God. But it is evident that a man possesses lawfully the price of a dog he has lawfully sold. Therefore it is not lawful to make an oblation of whatever we possess lawfully.
Objection 3: Further, it is written (Malachi 1:8): "If you offer the lame and the sick, is it not evil?" Yet an animal though lame or sick is a lawful possession. Therefore it would seem that not of every lawful possession may one make an oblation.
On the contrary, It is written (Prov.3:9): "Honor the Lord with thy substance." Now whatever a man possesses lawfully belongs to his substance. Therefore he may make oblations of whatever he possesses lawfully.
I answer that, As Augustine says (De Verb. Dom. Serm. cxiii), "shouldst thou plunder one weaker than thyself and give some of the spoil to the judge, if he should pronounce in thy favor, such is the force of justice that even thou wouldst not be pleased with him: and if this should not please thee, neither does it please thy God." Hence it is written (Ecclus.34:21): "The offering of him that sacrificeth of a thing wrongfully gotten is stained." Therefore it is evident that an oblation must not be made of things unjustly acquired or possessed. In the Old Law, however, wherein the figure was predominant, certain things were reckoned unclean on account of their signification, and it was forbidden to offer them. But in the New Law all God's creatures are looked upon as clean, as stated in Titus 1:15: and consequently anything that is lawfully possessed, considered in itself, may be offered in oblation. But it may happen accidentally that one may not make an oblation of what one possesses lawfully; for instance if it be detrimental to another person, as in the case of a son who offers to God the means of supporting his father (which our Lord condemns, Mat.15:5), or if it give rise to scandal or contempt, or the like.
Reply to Objection 1: In the Old Law it was forbidden to make an offering of the hire of a strumpet on account of its uncleanness, and in the New Law, on account of scandal, lest the Church seem to favor sin if she accept oblations from the profits of sin.
Reply to Objection 2: According to the Law, a dog was deemed an unclean animal. Yet other unclean animals were redeemed and their price could be offered, according to Lev.27:27, "If it be an unclean animal, he that offereth it shall redeem it." But a dog was neither offered nor redeemed, both because idolaters used dogs in sacrifices to their idols, and because they signify robbery, the proceeds of which cannot be offered in oblation. However, this prohibition ceased under the New Law.
Reply to Objection 3: The oblation of a blind or lame animal was declared unlawful for three reasons. First, on account of the purpose for which it was offered, wherefore it is written (Malach.1:8): "If you offer the blind in sacrifice, is it not evil?" and it behooved sacrifices to be without blemish. Secondly, on account of contempt, wherefore the same text goes on (Malach.1:12): "You have profaned" My name, "in that you say: The table of the Lord is defiled and that which is laid thereupon is contemptible." Thirdly, on account of a previous vow, whereby a man has bound himself to offer without blemish whatever he has vowed: hence the same text says further on (Malach.1:14): "Cursed is the deceitful man that hath in his flock a male, and making a vow offereth in sacrifice that which is feeble to the Lord." The same reasons avail still in the New Law, but when they do not apply the unlawfulness ceases.