If you help a poor person in the Name of the Lord, you are making a gift and at the same time granting a loan. You are making a gift because you have no expectation of being reimbursed by that poor person. You are granting a loan because the Lord will settle the account.
It is not much that the Lord receives by means of the poor, but He will pay a great deal on their behalf.
Let us lend to God almsgiving so we may receive from him clemency in exchange. Oh, how wise is this statement! “Whoever has mercy upon the poor lends to God.” Why did he not say, “Whoever has mercy upon the poor gives to God” instead of “lends”? Scripture recognizes our greediness; it understood that our insatiate desire, which looks longingly toward greediness, asks for an excess. This is why it did not say simply, “Whoever has mercy upon the poor gives to God,” so you may not think that the recompense will be customary; rather, it said, “Whoever has mercy upon the poor lends to God.” Since God borrows from us, then, he is our debtor. How do we want to have him, as judge or debtor? The debtor is ashamed before his lender; the judge does not put to shame the one who borrows.
The lesson, therefore, which he teaches us is love for the poor, which is precious in the sight of God. Do you feel pleasure in being praised when you have any friends or relatives feasting with you? I tell you of something far better: angels shall praise your bounty, and the rational powers above, and holy men as well; and he too shall accept it who transcends all, and who loves mercy and is kind. Lend to him fearing nothing, and you will receive with interest whatever you gave, for “he,” it says, “who has pity on the poor lends unto God.”
If a trustworthy man said to you, Give me one gold coin, and I will repay you one hundred solid gold coins, would you not gladly give him the one in order that you might receive the hundred? Now the God of heaven and earth says to you, “He who has compassion on the poor lends to God”; moreover, “As long as you did it for one of the least of these, you did it for me”; and in the Psalms, “Well for the man who is gracious and lends.” How much more, then, should you lend to God on earth, in order that you may receive a manifold return in eternal life? Then you will deserve to come before the tribunal of the eternal judge in the sight of the angels and can say with assurance and a clear conscience, Give, Lord, because I have given; have mercy because I have shown mercy.
"He who has mercy on the poor lends to the Lord," etc. The Lord himself proves the truth of this statement, when he predicts that he will say to those who give alms: "Insofar as you did it to one of these least of my brethren, you did it to me" (Matt. XXV). "Discipline your son, lest you despair; but do not set your heart on putting him to death." Be diligent in chastising any subject whom you see erring. But if he refuses correction, act towards him with such caution and temperance that he may find nothing in your words or actions wherewith he might sin more. The following also supports this sense:
[AD 379] Basil of Caesarea on Proverbs 19:17
It is not much that the Lord receives by means of the poor, but He will pay a great deal on their behalf.