Objection 1. It would seem that one who is under another's power can give alms. For religious are under the power of their prelates to whom they have vowed obedience. Now if it were unlawful for them to give alms, they would lose by entering the state of religion, for as Ambrose [The quotation is from the works of Ambrosiaster. Cf. Ondex to ecclesiastical authorities quoted by St. Thomas] says on 1 Timothy 4:8: "'Dutifulness [Douay: 'godliness'] is profitable to all things': The sum total of the Christian religion consists in doing one's duty by all," and the most creditable way of doing this is to give alms. Therefore those who are in another's power can give alms.
Objection 2. Further, a wife is under her husband's power (Genesis 3:16). But a wife can give alms since she is her husband's partner; hence it is related of the Blessed Lucy that she gave alms without the knowledge of her betrothed ["Sponsus" The matrimonial institutions of the Romans were so entirely different from ours that "sponsus" is no longer accurately rendered either "husband" or "betrothed."] Therefore a person is not prevented from giving alms, by being under another's power.
Objection 3. Further, the subjection of children to their parents is founded on nature, wherefore the Apostle says (Ephesians 6:1): "Children, obey your parents in the Lord." But, apparently, children may give alms out of their parents' property. For it is their own, since they are the heirs; wherefore, since they can employ it for some bodily use, it seems that much more can they use it in giving alms so as to profit their souls. Therefore those who are under another's power can give alms.
Objection 4. Further, servants are under their master's power, according to Titus 2:9: "Exhort servants to be obedient to their masters." Now they may lawfully do anything that will profit their masters: and this would be especially the case if they gave alms for them. Therefore those who are under another's power can give alms.
On the contrary, Alms should not be given out of another's property; and each one should give alms out of the just profit of his own labor as Augustine says (De Verb. Dom. xxxv, 2). Now if those who are subject to anyone were to give alms, this would be out of another's property. Therefore those who are under another's power cannot give alms.
I answer that, Anyone who is under another's power must, as such, be ruled in accordance with the power of his superior: for the natural order demands that the inferior should be ruled according to its superior. Therefore in those matters in which the inferior is subject to his superior, his ministrations must be subject to the superior's permission.
Accordingly he that is under another's power must not give alms of anything in respect of which he is subject to that other, except in so far as he has been commissioned by his superior. But if he has something in respect of which he is not under the power of his superior, he is no longer subject to another in its regard, being independent in respect of that particular thing, and he can give alms therefrom.
Reply to Objection 1. If a monk be dispensed through being commissioned by his superior, he can give alms from the property of his monaster, in accordance with the terms of his commission; but if he has no such dispensation, since he has nothing of his own, he cannot give alms without his abbot's permission either express or presumed for some probable reason: except in a case of extreme necessity, when it would be lawful for him to commit a theft in order to give an alms. Nor does it follow that he is worse off than before, because, as stated in De Eccles. Dogm. lxxi, "it is a good thing to give one's property to the poor little by little, but it is better still to give all at once in order to follow Christ, and being freed from care, to be needy with Christ."
Reply to Objection 2. A wife, who has other property besides her dowry which is for the support of the burdens of marriage, whether that property be gained by her own industry or by any other lawful means, can give alms, out of that property, without asking her husband's permission: yet such alms should be moderate, lest through giving too much she impoverish her husband. Otherwise she ought not to give alms without the express or presumed consent of her husband, except in cases of necessity as stated, in the case of a monk, in the preceding Reply. For though the wife be her husband's equal in the marriage act, yet in matters of housekeeping, the head of the woman is the man, as the Apostle says (1 Corinthians 11:3). As regards Blessed Lucy, she had a betrothed, not a husband, wherefore she could give alms with her mother's consent.
Reply to Objection 3. What belongs to the children belongs also to the father: wherefore the child cannot give alms, except in such small quantity that one may presume the father to be willing: unless, perchance, the father authorize his child to dispose of any particular property. The same applies to servants.
Hence the Reply to the Fourth Objection is clear.
Source: Summa Theologica (New Advent)