Summa Theologica I-II, q. 105: Of the Reason for the Judicial Precepts
Again, with regard to the greatness of a sin, four degrees may be observed, even in respect of one single deed. The first is when a sin is committed unwillingly; because then, if the sin be altogether involuntary, man is altogether excused from punishment; for it is written (Dt. 22:25, seqq.) that a damsel who suffers violence in a field is not guilty of death, because "she cried, and there was no man to help her." But if a man sinned in any way voluntarily, and yet through weakness, as for instance when a man sins from passion, the sin is diminished: and the punishment, according to true judgment, should be diminished also; unless perchance the common weal requires that the sin be severely punished in order to deter others from committing such sins, as stated above. The second degree is when a man sins through ignorance: and then he was held to be guilty to a certain extent, on account of his negligence in acquiring knowledge: yet he was not punished by the judges but expiated his sin by sacrifices. Hence it is written (Lev. 4:2): "The soul that sinneth through ignorance," etc. This is, however, to be taken as applying to ignorance of fact; and not to ignorance of the Divine precept, which all were bound to know. The third degree was when a man sinned from pride, i.e. through deliberate choice or malice: and then he was punished according to the greatness of the sin [*Cf. Dt. 25:2]. The fourth degree was when a man sinned from stubbornness or obstinacy: and then he was to be utterly cut off as a rebel and a destroyer of the commandment of the Law [*Cf. Num. 15:30,31].
Accordingly we must say that, in appointing the punishment for theft, the Law considered what would be likely to happen most frequently (Ex. 22:1-9): wherefore, as regards theft of other things which can easily be safeguarded from a thief, the thief restored only twice their value. But sheep cannot be easily safeguarded from a thief, because they graze in the fields: wherefore it happened more frequently that sheep were stolen in the fields. Consequently the Law inflicted a heavier penalty, by ordering four sheep to be restored for the theft of one. As to cattle, they were yet more difficult to safeguard, because they are kept in the fields, and do not graze in flocks as sheep do; wherefore a yet more heavy penalty was inflicted in their regard, so that five oxen were to be restored for one ox. And this I say, unless perchance the animal itself were discovered in the thief's possession: because in that case he had to restore only twice the number, as in the case of other thefts: for there was reason to presume that he intended to restore the animal, since he kept it alive. Again, we might say, according to a gloss, that "a cow is useful in five ways: it may be used for sacrifice, for ploughing, for food, for milk, and its hide is employed for various purposes": and therefore for one cow five had to be restored. But the sheep was useful in four ways: "for sacrifice, for meat, for milk, and for its wool." The unruly son was slain, not because he ate and drank: but on account of his stubbornness and rebellion, which was always punished by death, as stated above. As to the man who gathered sticks on the sabbath, he was stoned as a breaker of the Law, which commanded the sabbath to be observed, to testify the belief in the newness of the world, as stated above (Q[100], A[5]): wherefore he was slain as an unbeliever.
Reply to Objection 10The Old Law inflicted the death penalty for the more grievous crimes, viz. for those which are committed against God, and for murder, for stealing a man, irreverence towards one's parents, adultery and incest. In the case of thefts of other things it inflicted punishment by indemnification: while in the case of blows and mutilation it authorized punishment by retaliation; and likewise for the sin of bearing false witness. In other faults of less degree it prescribed the punishment of stripes or of public disgrace.
The punishment of slavery was prescribed by the Law in two cases. First, in the case of a slave who was unwilling to avail himself of the privilege granted by the Law, whereby he was free to depart in the seventh year of remission: wherefore he was punished by remaining a slave for ever. Secondly, in the case of a thief, who had not wherewith to make restitution, as stated in Ex. 22:3.
The punishment of absolute exile was not prescribed by the Law: because God was worshipped by that people alone, whereas all other nations were given to idolatry: wherefore if any man were exiled from that people absolutely, he would be in danger of falling into idolatry. For this reason it is related (1 Kings 26:19) that David said to Saul: "They are cursed in the sight of the Lord, who have cast me out this day, that I should not dwell in the inheritance of the Lord, saying: Go, serve strange gods." There was, however, a restricted sort of exile: for it is written in Dt. 19:4 [*Cf. Num. 35:25] that "he that striketh [Vulg.: 'killeth'] his neighbor ignorantly, and is proved to have had no hatred against him, shall flee to one of the cities" of refuge and "abide there until the death of the high-priest." For then it became lawful for him to return home, because when the whole people thus suffered a loss they forgot their private quarrels, so that the next of kin of the slain were not so eager to kill the slayer.
Reply to Objection 11Dumb animals were ordered to be slain, not on account of any fault of theirs; but as a punishment to their owners, who had not safeguarded their beasts from these offenses. Hence the owner was more severely punished if his ox had butted anyone "yesterday or the day before" (in which case steps might have been taken to prevent its butting suddenly). Or again, the animal was slain in detestation of the sin; and lest men should be horrified at the sight thereof.
Reply to Objection 12The literal reason for this commandment, as Rabbi Moses declares (Doct. Perplex. iii), was because the slayer was frequently from the nearest city: wherefore the slaying of the calf was a means of investigating the hidden murder. This was brought about in three ways. In the first place the elders of the city swore that they had taken every measure for safeguarding the roads. Secondly, the owner of the heifer was indemnified for the slaying of his beast, and if the murder was previously discovered, the beast was not slain. Thirdly, the place, where the heifer was slain, remained uncultivated. Wherefore, in order to avoid this twofold loss, the men of the city would readily make known the murderer, if they knew who he was: and it would seldom happen but that some word or sign would escape about the matter. Or again, this was done in order to frighten people, in detestation of murder. Because the slaying of a heifer, which is a useful animal and full of strength, especially before it has been put under the yoke, signified that whoever committed murder, however useful and strong he might be, was to forfeit his life; and that, by a cruel death, which was implied by the striking off of its head; and that the murderer, as vile and abject, was to be cut off from the fellowship of men, which was betokened by the fact that the heifer after being slain was left to rot in a rough and uncultivated place.
Mystically, the heifer taken from the herd signifies the flesh of Christ; which had not drawn a yoke, since it had done no sin; nor did it plough the ground, i.e. it never knew the stain of revolt. The fact of the heifer being killed in an uncultivated valley signified the despised death of Christ, whereby all sins are washed away, and the devil is shown to be the arch-murderer.