פּירוש אויף שמות 22:24

אם כסף תלוה את עמי IF THOU LEND MONEY TO ANY OF MY PEOPLE — R. Yishmael said: wherever אם occurs in Scripture it is used of an act the performance of which is optional, except in three instances, of which this is one (Mekhilta; cf. Rashi on Exodus 20:22 - the translation therefore is: “When thou lendeth etc.”).

אם כסף, the reason why the law to extend loans to the needy has been written here is that the three categories of people mentioned previously, i.e. the proselyte, the orphan and the widow are the ones most in need of borrowing money.

אם כסף תלוה, “if you lend money, etc.;” Rabbi Yehudah hachassid says that the reason this verse commences with the word אם, “if,” instead the word כאשר, “when,” is that there are occasions when this is not a commandment but something that is voluntary, such as when the borrower has a reputation of not repaying a loan.