DEUT717 It is a positive commandment to give alms to the poor of Israel, according to what is fitting for them, if the giver can afford it, as it is said, "You shall surely open your hand unto him" (Deuteronomy 15:8), and again, "Then you shall uphold him; as a stranger and a settler shall he live with you… That your brother may live with you" (Leviticus 25:35-6). He who seeing a poor man begging turns his eyes away from him and fails to give him alms, transgresses a negative commandment, as it is said (this verse). You are commanded to give the poor man according to what he lacks. If he has no clothing, he should be clothed. If he has no house furnishings, they should be bought for him. If he has no wife, he should be helped to marry. If it is a woman, she should be given in marriage. Even if it had been his wont to ride a horse, with a man servant running in front of him, and he has now become poor and has lost his possessions, one must buy him a horse to ride and a man servant to run before him, as it is said, "Sufficient for his need in that which he needs" (Deuteronomy 15:8). You are thus obligated to fill his want; you are not, however, obligated to restore his wealth.… If the poor man comes forth and asks for enough to satisfy his want, and if the giver is unable to afford it, the latter may give him as much as he can afford. How much is that? In choice performance of this religious duty, up to one-fifth of his possessions; in middling performance, up to one-tenth of his possessions; less than this brands him as a person of evil eye. At all times one should not commit himself to give less than one-third of a shekel per year. He who gives less than this has not fulfilled this commandment at all. Even a poor man who lives entirely on alms must himself give alms to another poor man. Moses Maimonides Mishneh Torah -- The Book of Agriculture.