In Jewish tradition, tzedakah, or acts of justice, is considered a divine commandment that Jews have an obligation to observe. Tzedakah is a matter of justice and therefore a legislative obligation. You are obligated to be generous to those in need whether you feel like it or not.
One who does not give tzedakah to the needy is not simply uncharitable of heart, but in violation of the law.
Rabbi Rami Shapiro, founder of the Simply Jewish Fellowship