Giving Him a loan

The pasuk says; “asser t’asser” – give masser so that you shall become rich / so that you will be able to give masser again (-two explanations in the Rishonim). One is even allowed to test Hashem about this promise, although normally testing Hashem is a Torah prohibition. So why is testing Hashem permitted here? One answer is that when one gives tzeddaka or massaer he  is actually lending  Hashem money! “He who gives a poor man is lending Hashem!”, says the Torah. (Hashem takes personal financial responsibility for the down-and-out) And certainly, if hashem borrows, He pays back! Usually we do not test Hashem for our reward is waiting in the next world, and we have no right to expect it now. However, money we “lend” Hashem will certainly be paid back in this world, – where the money was borrowed. (Sefer Hachinuch)