Rosh HaYeshiva, Kerem B'Yavneh
In our parsha there are a number of mitzvot and prohibitions regarding the mitzvah of tzedaka:
Regarding the tithe of the poor it says: "Then the Levite can come ... and the proselyte, the orphan, and the widow ... so they may eat and be satisfied." (Devarim 14:29)
Regarding charity: "You shall not harden your heart or close your hand against your destitute brother. Rather, you shall open you hand to him." (Devarim 15:7-8)
Regarding shemitta: "Beware lest there be a lawless thought in your heart saying, 'The seventh year approaches, the remission year,' and you will look malevolently upon your destitute brother and refuse to give him ... and it will be a sin upon you." (Devarim 15:9)
To us it appears that the possessions that are in our hands are ours, and we are doing a favor to the poor person when we give him of our property. However, the Torah teaches us that all the money that is in a person's hands is only a means and a tool by which a person fulfills his role in this world, and any usage of property that we received from the Creator for a self-serving purpose is nothing but stealing.
On Yom Kippur we conclude the prayers with the request, "so that we should refrain from stealing." This is surprising; why is only the transgression of stealing mentioned at the end of the day? However, the intention is not to the prohibition against stealing from others, but rather to improper use of the property that G-d places in our hands for us to use as tools in His service. When we do not sustain the poor and use G-d's present only for our personal needs, we are stealing that property from G-d.
The rich person who is an egoist, who sees in money an independent goal, will never find fulfillment. Therefore, money is called "kesef," for the word "kisufim" (longing), since a person longs it and will not be satisfied with it. One who has a hundred wants two hundred, etc. (Kohelet Rabbah 1:34) Similarly, the Maharal explains that the word "zahav" (gold) is from the phrase "zeh hav" (Give this!), for he always seeks to receive, and he is always lacking. Therefore the destitute person is called an "evyon," because he always desires ("ta'ev") to get more and more. Therefore, the truly rich person is one who is happy with his share, and not necessarily one who has a lot, because one who has desires to receive more, and therefore he is poor.
The halacha is that the owner of a field is not allowed to cut the pe'ah and give it to the poor, but rather he must allow the poor to enter the field and cut the pe'ah himself. Rav Kook zt"l explains that this is to indicate that the owner of the field is not the true owner of the pe'ah, and therefore he may not act like an owner. Rather, the pe'ah is given to the poor person, and he is the owner of the field with regard to the pe'ah, and therefore he enters the field and reaps.
Parshat Re'eh is read on Shabbat Mevarchim Elul -- before the seventh month, the Sabbatical month, in which G-d releases the debt of Bnei Yisrael and atones for them -- because He acts towards us with kindness and mercy. We must act to each other with kindness, and then G-d will also act with us accordingly. "To You, G-d, is righteousness" -- when we give charity; but if we say, "The seventh year approaches," and we do not open our hand to the destitute -- also our debts toward G-d will not be released. G-d's relationship with a person is linked to the relationship between man and his friend, and therefore we find in the seforim two acronyms for the month of Elul:
"Ani Ledodi Vedodi Li." "I am My Beloved's and My Beloved is mine." (Shir Hashirim 6:3)
"Ish Lere'eihu Umatanot La'evyonim." "[Sending delicacies] one to another, and gifts to the poor." (Esther 9:22)
Therefore, Chazal say that in these days of the month of Elul there is a need to increase in acts of chesed and charity, and this brings to the general redemption: "Zion will be redeemed though justice, and those who return to her through righteousness." (Yeshaya 1:27)