“You shall tithe all the produce of your fields” (Devarim 14:22).
The Talmud interprets the word תעשר, “You shall tithe,” to mean תעשיר, that “you may become wealthy,” and according to this interpretation, the Torah promises material reward for tithing (Shabbat 119). One might think that by giving Tzedaka one is depleting his assets. Not so, says the Torah. Giving Tzedaka does not impoverish, but on the contrary, one receives much more than he gives.
The Chafetz Chaim illustrates the point of withholding Tzedaka through a parable. A peasant brought his farm produce to the market. In order to determine the amount of the sale, he had the buyer put a coin into a container for each bundle of grain that was delivered, so that by counting the coins they would know the number of bundles purchased. When the merchant’s attention was diverted, the peasant stole several coins from the container, not realizing that with each coin he stole he lost the price of a bundle of grain. The small gain by theft was far offset by the loss of payment for his merchandise.
The Chafetz Chaim says that one may think that by refraining from giving Tzedaka one is saving money. One does not realize that the gain of giving Tzedaka outweighs the loss.
We often measure gain or loss by our consideration of what is the immediate, short-term gain or loss. This is not the way a shrewd financier operates. With Tzedaka, as with many other Mitzvot, making a short-term expenditure in order to achieve a long-term gain is a wise investment.