“You shall not give him your money for interest, nor give him your food for increase!” (Vayikra 25:37)
It is a negative commandment that one may not lend at interest to a Jew, as it says “You shall not give him your money for interest, nor give him your food for increase!”. These are not two separate prohibitions. Rather, they are the same prohibition expressed in two different ways. This is the way of the Torah that many times interdictions are repeated, especially when it is discussing things which Hashem wanted us to keep a long way away from. The Torah also warns us many times about those things which we have to be very careful about, like people who warn each other about something dangerous, where they will repeat it many times and add many words about the topic, so that the person who has been warned will remember and be very careful about the matter. Even though a person should always be extremely careful about the words of Hashem, and listen to whatever He wants even if given only a very small allusion, it is one of the many kindnesses that He performs with His creations that He repeats certain prohibitions many times, like a man would warn his own son. For this we should thank Hashem for all of the wonderful kindnesses that He has done for us.
Amongst the roots of this commandment are that Hashem in His goodness, wanted that His chosen people should be able to live, so He commanded to remove the stumbling-block from their path, so that one Jew would not swallow up the fortune of his friend without the friend noticing until his house is completely empty, for that is the effect of interest as is well-known. It is for this reason that it is called “neshech” (which means bite).
This commandment applies in all places and at times, both to men and to women. One who sins and lends at interest has transgressed a biblical prohibition.