The commandment to give charity, tzedakah, nestles at the heart of the many divine commands given by God to the Jews immediately prior to entering the land of Israel.
Parashat Re'eh foregrounds the important idea that the Judaic hallmark of a just society is the constant obligation to care for the poor. The notion of charity-as-justice is a principle to which we are legally bound in Jewish law and it is misunderstood if construed only as compassionate caring or impulsive giving.
Despite the great significance of the mitzvah of tzedakah, it is intended neither to be limitless nor to become intolerable for the individual. Justice must work for both giver and receiver.
To this end, the Shulchan Aruch, the Code of Jewish Law, sets out three percentage categories depending on one's level of net income - one fifth, one tenth, or less than one tenth.