When you give to a needy person or for a worthy cause, it is no more than a loan. G‑d Himself is the guarantor.

Not only that, G‑d says: The more you give, the more you get—beyond what you've given.

The Talmud tells us that this is the only case in which we are allowed to test G‑d. Donate a tenth of your earnings, and you will earn far more.