The first Mishnah in Kiddushin (2a) teaches that a woman can be acquired in three ways: בכסף בשטר ובביאה – “With money, a document, or with marital relations.”
Why is money the first item mentioned in the Mishnah?
The Meiri brings two answers: 1) מפני שהוא ראש המדברים בכל מקום – “The one with money is always able to speak first.” 2) It is the first method mentioned in the pasuk, the pasuk says כי יקח, and we learn from here that money works for kiddushin.
Kesef or Shoveh Kesef
The Mishnah teaches that a woman becomes mekudeshes [betrothed] through kesef [money] or shaveh kesef [an item with monetary value]. Accordingly, a man may give a coin to a woman for kiddushin. The Rema (Even HaEzer 27:1) writes, however, that the present practice is not to give a coin for kiddushin, but to give a ring. What is the reason for this practice?
Question and Answer of the Avnei Miluim
The Avnei Miluim (siman 27:2) points out that there is no Mordechai which discusses this, and seemingly the Beis Shmuel is referring to a Hagaos Mordechai. However, this is still difficult as the Hagaos Mordechai (Kiddushin 488), does not write that one should not use a coin. Rather, he questions why a coin may be used for kiddushin. The Gemara in Kiddushin (8a) explains that if a woman thinks that the object which the man gives is of a certain value and the object is of a different value, the kiddushin does not take effect. The Gemara in Bava Metzia (45b) rules that a coin may not be used to make a kinyan chalipin because the value which a person ascribes to a coin is the stamp or form on the coin (since the coin is unusable without the stamp), but the stamp on the coin often changes (such as when a new king is appointed), and thus it may not be used for a kinyan chalipin. Accordingly, one also should not be permitted to use a coin for kiddushin, since the woman relies on the stamp, and the stamp will change.
Although the Hagaos Mordechai raises this question, he does not discourage the use of a coin for kiddushin. Additionally, the Avnei Miluim cites various Gemara’s where we see clearly that money may be used.
The Avnei Milu'im answers the question of the Hagaos Mordechai based on the words of Rashi in Bava Metzia (45b, d.h. Matbe'a). Rashi writes that a coin without a stamp may not be used for kinyan chalipin because chalipin must be performed with a complete object. A coin without a stamp is an incomplete object. According to Rashi, the Gemara in Bava Metzia does not mean that the reason why a coin may not be used for a kinyan chalipin is that its true value is not what people assume it to be. Rather, the Gemara means that even when it bears its stamp (and its value is what people assume it to be), it is considered incomplete since the stamp might change tomorrow. With regard to kiddushin, this concern poses no problem because even an incomplete object may be used for kiddushin as long as it is worth a perutah. Since the coin with a stamp is worth what the woman thinks it is worth, the kiddushin takes effect.
He also cites the Nimukei Yosef who learns that the problem with using a coin with a stamp for chalipin is that by chalipin one wants the item to remain (רוצה בקיומו) and since the stamp on the coin often changes it is not suitable, however, by kiddushin there is no need for the item to remain, therefore, it is ok.
The Approach of the Sefer HaMakneh and the Rogatchover
The Sefer HaMakneh (Chiddushim to Even HaEzer 50:1) and the Tzofnas Pane’ach (Hilchos Ishus 3:1) point out that the custom to be mekadesh a woman with a ring may have been adopted when it became the practice to perform the nisu’in immediately after the kiddushin (instead of some months after the kiddushin). When the nisu’in is performed, all the wife's property becomes nichsei milug and the husband is entitled to its produce (peros). If the husband would give the wife money and then perform nisu'in immediately afterwards, the money would be worth much less to her since she would have rights only to the body (guf) of the coin and not to the peros (the spending value) of the coin.
Such a situation would be akin to a case in which the man tricked the woman about the amount of money he intended to give for kiddushin, or to a case in which the man keeps some of the amount for himself. Therefore, the Chachamim instituted the custom that the man gives a ring, an object which the woman wears. The Gemara in Kesubos (54a) teaches that a married woman retains the rights to the use (peros) of her clothing and personal objects. When she receives a ring, she receives the full value of the ring even when the nisu'in is performed immediately afterward. (The Tzofnas Pane'ach cites the Yerushalmi in Nazir 5:2 which states that a woman's jewelry is considered her possession and not the possession of her husband.)
The Chinuch
The sefer HaChinuch (Mitzvah 552) writes that the source for the practice to give a ring for kiddushin is the consideration to provide the woman with something which will be in front of her always and remind her of her devotion to her husband (as the pasuk says, “Tie them on your fingers, inscribe them on the tablet of your heart” (Mishlei 7:3), a reference to the mitzvos of the Torah).
Additional Reasons
The Likutei Maharich (Hanhagos Yom Chuppah) explains that a ring is something that connects two things together, like we find by the keroshim in the Mishkan, that every two keroshim had a ring above them connecting them, the same was with the choshen and the ephod. Therefore, we perform kiddushin with a ring to hint to the fact that through kiddushin, there should be a connection between the husband and wife.
Some say, a ring is round and has no ends, this hints at the fact that the covenant between husband and wife should be an everlasting covenant with no end.
The Biur HaGra based on the Tikunei Zohar (Tikkun 5) says that the ring is closed on all sides, and this hints to the fact that the woman is now prohibited to the entire world.
The Rema himself cites the Tikunei Zohar (beginning of Tikun 5, and Tikun 10, page 25b) as a source for the practice to give a ring for kiddushin.
In the times when kiddushin and nisu’in were separate, the woman had rights to both the guf [body] and the peros [fruits] between the kiddushin and nisu’in and if she wanted, she could spend the money. However, nowadays there is no gap between the kiddushin and nisu’in and once she becomes a nesuah, she only has a right to the guf and not the peros. Since she doesn’t have any rights to the peros she isn’t able to spend the money, and all she can do is keep it without spending it, which isn’t worth very much.
