גזירה שוה

Every morning at the beginning of our Davening, we recite the thirteen methods of deriving Torah law, according to Rabbi Yishmael. These methods were given on Mount Sinai, as part of the Oral Law. These derivations, have the status of Torah laws, and are binding. One of these thirteen methods, is called גזירה שוה. One is not permitted to invent a גזירה שוה, as these must also originate on הר סיני. The גזירה שוה refers to a situation where the same word is used in two different instances, and there is a common denominator between the two. Parshat חיי שרה had one of the more well known Gezeira Shave’s. It is referred to as קיחה קיחה משדה עפרון. The purchase of מערת המכפילה has the usage of the words, לקח את השדה, that Avraham “took” the Cave of Machpeila. And it is clear that “taking” meant that he purchased it with money. In the Book of Devarim, the Torah discusses marriage with the words, כי יקח איש אשה, when a man takes a woman. The גזירה שוה principle teaches that “taking” refers to money. Therefore, we learn that when a man takes a wife, he must give her something that has monetary value. (There are other methods of marriage, but this is how marrying with כסף is learned. This is the example of גזירה שוה as taught by רבי ישמעאל.