"Speak to the Children of Israel and let them take for Me a portion" [Terumah 25:2]
Why does the verse state "take for Me a portion" and not "give Me a portion"?
The Torah is showing us the greatness vested in the mitzvah of giving tzedakah. When we fulfill the mitzvah of tzedakah, it may appear as if we are giving, but in truth we are actually taking (receiving) for ourselves a very great mitzvah.
The Midrash Rabbah elaborates on this idea: "More than what the host does for the poor man, the poor man does for the host". The host may have given the poor person a perutah for tzedakah, but the poor person has enabled the host to earn a mitzvah that is more valuable than "thousands in gold and silver" [Tehillim 119:72].
Someone who refuses to assist a poor person, said the Chofetz Chaim, can be compared to a farmer who piled up his wagon with wheat and then travelled to a large city in order to sell it. When the farmer arrived at the city, he was immediately met by dozens of eager customers waiting to purchase his produce.
He was afraid, however, that the customers would attempt to deceive him by taking bundles of wheat without paying for them. He therefore told them "Go ahead and fill your bags with wheat. But each time you fill up a bag, place one copper coin into my hat. When you finish filling your sacks, we will count the coins in my hat, and that way we will know how many sacks you have to pay for."
The customers agreed to the farmer's method and followed his instructions. The farmer's hat was soon full of shiny copper coins.
The farmer saw all the coins in his hat and was overcome by temptation. He quickly stole some of the coins and put them in his pocket.
How foolish is that farmer! remarked the Chofetz Chaim. He may have managed to swipe a few coins, but he will lose much more than he gained because when the time comes to pay for the wheat and the coins are counted, there will be less coins than sacks, and he will lose the payment for all those sacks. This foolish farmer will lose the payment of an entire sack of wheat for every coin that he took for himself.
This is also the case, said the Chofetz Chaim, when someone refuses to give tzedakah. He may hold on to a coin or two, but he will lose the immense reward from a mitzvah that could have been his.
Source: Rabbi Y. Bronstein