"let each one give [וְנָתְנוּ] to the Lord an atonement for his soul "[Ki Tisa 30:12]
The Ba'al HaTurim notes that the word וְנָתְנוּ is a palindrome: it can be read both backwards and forwards. This is to teach us that whatever a person donates to tzedakah will ultimately be returned to him: one never loses by giving charity.
There was a rich man in Volozhin who used to give generously to the poor of his city. Misfortune struck, however, and he lost much of his wealth.
He approached R' Chaim of Volozhin with the following question: "Rebbe" he said, "I do not know what to do. As you know, I used to give a large sum of money each month to the poor people of Volozhin. Due to the hard times which have befallen me, however, I don't have that much money to give. Should I simply give a smaller sum than I have in the past, or should I borrow money from others and give the same amount that I am accustomed to giving?"
R' Chaim thought for a moment and then responded: "Continue to give the exact amount that you have always given. As far as your livelihood is concerned, do not worry, for Hashem will provide you with all that you need."
A few weeks later, the man returned to R' Chaim, but now he was happy. "Rebbe" he said, "your words have been fulfilled! I did exactly as you said: I borrowed money and distributed it to the poor. Shortly thereafter, I participated in a lottery and won an enormous sum of money."
Source: Rabbi Yisrael Bronstein