A Guarantee For Wealth:
The Gemara (Shabbos 119A) states: “Aser te’aser... Give ma’aser so that you will become rich.”
The Kedushas Levi explains that when a person gives money to tzedakah, the money goes up to Shomayim and stands before Hashem. For example, if a person gives one coin to charity, that money goes up to the Heavens. Hashem looks at it and says: This man gave one coin to tzedakah because he had 10. Hashem considers it as if the person did a mitzvah with all 10 coins, as all of the coins were part of the impetus for the tzedakah. In this merit, Hashem rewards him with the ability to give 10 coins to tzedakah the next year, by giving him 100 coins.
Thus, the pasuk is saying: “Aser” – if one gives a tenth of his money to tzedakah. “Te’aser es kol tevuas zarecha” – the next year, he will give an amount of ma’aser that equals all of this year’s crops.
The Noam Elimelech writes a similar explanation. He quotes the Mishnah (Avos 4:2) that says: “The reward for a mitzvah is (another) mitzvah”, and explains that if someone gives ma’aser, Hashem rewards him by giving him the means to give ma’aser again. He adds that the pasuk is saying that if one gives ma’aser one year, the next year Hashem will give him enough crops to give “kol tevuas zarecha”, the amount of ma’aser that is equal to the entire crop of the previous year – meaning that his income will increase 100 times over the previous year. The pasuk concludes by saying that the same will occur “year by year”.
