Objection 1. It would seem that almsgiving is not an act of charity. For without charity one cannot do acts of charity. Now it is possible to give alms without having charity, according to 1 Corinthians 13:3: "If I should distribute all my goods to feed the poor... and have not charity, it profiteth me nothing." Therefore almsgiving is not an act of charity.
Objection 2. Further, almsdeeds are reckoned among works of satisfaction, according to Daniel 4:24: "Redeem thou thy sins with alms." Now satisfaction is an act of justice. Therefore almsgiving is an act of justice and not of charity.
Objection 3. Further, the offering of sacrifices to God is an act of religion.
But almsgiving is offering a sacrifice to God, according to Hebrews 13:16: "Do not forget to do good and to impart, for by such sacrifices God's favor is obtained." Therefore almsgiving is not an act of charity, but of religion.
Objection 4. Further, the Philosopher says (Ethic. iv, l) that to give for a good purpose is an act of liberality. Now this is especially true of almsgiving. Therefore almsgiving is not an act of charity.
On the contrary, It is written 1 John 3:17: "He that hath the substance of this world, and shall see his brother in need, and shall put up his bowels from him, how doth the charity of God abide in him?"
I answer that, External acts belong to that virtue which regards the motive for doing those acts. Now the motive for giving alms is to relieve one who is in need. Wherefore some have defined alms as being "a deed whereby something is given to the needy, out of compassion and for God's sake," which motive belongs to mercy, as stated above (30, 1,2). Hence it is clear that almsgiving is, properly speaking, an act of mercy. This appears in its very name, for in Greek eleemosyne it is derived from having mercy eleein even as the Latin "miseratio" is. And since mercy is an effect of charity, as shown above (30, 2, 3, Objection 3), it follows that almsgiving is an act of charity through the medium of mercy.
Reply to Objection 1. An act of virtue may be taken in two ways: first materially, thus an act of justice is to do what is just; and such an act of virtue can be without the virtue, since many, without having the habit of justice, do what is just, led by the natural light of reason, or through fear, or in the hope of gain. Secondly, we speak of a thing being an act of justice formally, and thus an act of justice is to do what is just, in the same way as a just man, i.e. with readiness and delight, and such an act of virtue cannot be without the virtue.
Accordingly almsgiving can be materially without charity, but to give alms formally, i.e. for God's sake, with delight and readiness, and altogether as one ought, is not possible without charity.
Reply to Objection 2. Nothing hinders the proper elicited act of one virtue being commanded by another virtue as commanding it and directing it to this other virtue's end. It is in this way that almsgiving is reckoned among works of satisfaction in so far as pity for the one in distress is directed to the satisfaction for his sin; and in so far as it is directed to placate God, it has the character of a sacrifice, and thus it is commanded by religion.
Wherefore the Reply to the Third Objection is evident.
Reply to Objection 4. Almsgiving belongs to liberality, in so far as liberality removes an obstacle to that act, which might arise from excessive love of riches, the result of which is that one clings to them more than one ought.
Source: Summa Theologica (New Advent)