The Torah in Parashat Behar (Vayikra 25:14) introduces the laws of “Mekah U’memkar” – “buying and selling.” The Sefer Ha’hinuch lists as the 336 th Biblical command the requirement for Bet Din to apply the principles of Torah law when adjudicating cases involving monetary transactions. He explains that the Torah commands following this system because an effective and just legal system is critical for maintaining law and order, and peaceful relations among people. The Sefer Ha’hinuch elaborates on a number of principles relevant to the Torah’s laws governing transactions, including the distinction drawn by Halacha between real estate and moveable possessions. Real estate is transacted in three ways: “Kessef” – the transfer of money; “Shetar” – transferring a valid sale contract; and “Hazaka” – the buyer’s performing certain actions that demonstrate ownership. Once a buyer and seller agree on the deal, any one of these three measures suffices to transfer the property in question to the buyer’s ownership. When it comes to moveable items, different methods effect the transaction in different situations. Some items are transacted through “Hagbeha” – lifting the item; some through “Meshicha” – pulling the item; and other through Mesira – taking physical control over the item. Lightweight items, as a rule, are transacted through “Hagbeha,” but a boat, for example, which obviously cannot be lifted, is transacted through “Mesira” – handing over the ropes to the buyer. The Sefer Ha’hinuch follows the view that all these methods of acquisition for Metaltelin (moveable items) were enacted by the Sages. On the level of Torah law, only the transfer of money effects the transfer of ownership, and nothing else is needed. However, the Sages enacted that a sold item does not become the buyer’s legal property until he physically takes possession of it, through the methods mentioned above. The Sages enacted this provision out of concern that after the buyer pays the seller for the item, the seller will not properly guard it, because he already received the money and thus does not care what happens to the item. In order to protect buyers, the Sages legislated that purchased items remain the seller’s property until the buyer takes physical possession, as discussed. An interesting question arises according to this view with regard to Kiddushin – the act whereby a bride becomes Halachically betrothed to the groom. This is done through the groom’s transfer of something he owns – generally a ring – to the bride. In a case where the groom purchased the ring but had yet to pay for it, we might wonder whether the Kiddushin is valid. Even though the groom took physical possession of the ring, nevertheless, this act is an effective means of legal acquisition only Mi’de’rabbanan – by force of Rabbinic enactment; according to Torah law, he does not acquire the ring until he pays the money. Seemingly, a Rabbinically-sanctioned acquisition should not suffice for the bride to be betrothed on the level of Torah law. This might be why some Rabbis have the practice of asking the groom just before the Kiddushin whether he paid for the ring with his own money, to ascertain that an acquisition was made on the level of Torah law. This Misva applies in all times and in all places, and is assigned to the judges of Bet Din. If they fail to follow these principles in adjudicating cases involving property transactions, they are in violation of this affirmative command. However, if the two parties agree to accept a decision that does not follow Torah law, the judges may reach a decision against the Torah’s rules. When it comes to monetary law, the litigants are permitted to agree to a different system of adjudication, and so when they do, the judges are not required to reach a decision based on the Torah’s system.