The Rama (Rabbi Moshe Isserles of Cracow, Poland, 1525-1572), in Eben Ha’ezer (31:2), records the custom to show the betrothal ring to the witnesses under the Hupa before the actual betrothal. Before the groom places the ring on the bride’s finger, the ring is shown to the witnesses and they are asked to confirm that it is "Shaveh Peruta" – worth the minimum value of a "Peruta." This is done to ensure that the bride does not think that the ring is worth more than its actual value. If, for example, the bride assumes the ring is worth $100, when in truth it is worth only $10, then the Kiddushin (betrothal) is made on incorrect assumptions and may thus be invalid. The witnesses therefore verbally declare that the ring is worth a "Peruta," to clarify to the bride that it might not be worth any more than that.
The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) notes that the witnesses should not make humorous comments about the ring when they are asked if it is "Shaveh Peruta." If they say, even jokingly, something to the effect of, "Sure, it’s worth much more than that," then the bride might expect the ring to be worth more than its real value, thus invalidating the Kiddushin. The witnesses should therefore say nothing more than, "Yes, it’s Shaveh Peruta."
The Shulhan Aruch (Eben Ha’ezer 28:17) writes that if a groom betroths the bride with a ring or with money that does not belong to him, the betrothal is invalid. The groom must therefore ensure that he owns the ring or coin with which he performs the Kiddushin. If his father purchased the ring or coin for him, the father must give it to him as a gift, so that the groom is the legal owner.
It is customary for the groom to place the ring specifically on the bride’s forefinger, meaning, the finger immediately next to the thumb. One reason for this custom is that the forefinger is the finger that people use most frequently, such as when they point to written text when teaching children. Therefore, placing the ring on the forefinger helps to publicize the Kiddushin to the greatest extent, informing everybody present that the bride has been betrothed.
Others explain this custom as a subtle allusion to the nineteenth chapter of Tehillim, which makes reference to marriage (verse 6 – "Ve’hu Ke’hatan Yoseh Me’hupato"). This chapter also contains five consecutive five-word phrases (verses 8-10), each of which has Hashem’s Name as its second word:
1) "Torat Hashem Temima Meshibat Nafesh"
2) "Edut Hashem Ne’emana Mahkimat Peti"
3) "Pikudeh Hashem Yesharim Mesameheh Leb"
4) "Misvat Hashem Bara Me’irat Enayim"
5) "Yir’at Hashem Tehora Omedet La’ad"
The five words in each phrase correspond to the five fingers on the hand, and the second word – Hashem’s Name – parallels the second finger on the hand, the forefinger. By placing the ring on the forefinger, the groom brings to mind the Name of Hashem which is the second word in these phrases which appear in a chapter of Tehillim that mentions marriage. Through marriage, a man and woman complete the Name of God. The letter "Yod" in the word "Ish" ("man") combines with the "Heh" in the word "Isha" ("woman") to form the divine Name of "Yod"-"Heh." The groom therefore places the ring on the bride’s forefinger to allude to the Name of Hashem which is completed through their marriage.
If the groom mistakenly placed the ring on a different finger, the betrothal is nevertheless valid.
Rav Moshe Feinstein (Russia-New York, 1895-1986), in his Iggerot Moshe (Eben Ha’ezer, vol. 3, Siman 18), rules that a bride and groom should not perform a "double ring ceremony" under the Hupa. It is customary among many non-Jews and non-observant Jews for the bride and groom to exchange rings at the wedding, as opposed to the traditional Jewish practice that only the groom gives a ring to the bride. There is absolutely no Halachic significance to a ring given by the bride to the groom, and doing so under the Hupa might violate the prohibition of imitating the practices of the gentiles. If the bride wants to give the groom a ring, she may give it to him after the Hupa ceremony, during the Yihud (seclusion). She should not give him a ring under the Hupa.
Summary: Before the groom gives the bride the ring or coin for the betrothal, it should be shown to the witnesses who affirm that it is worth a "Shaveh Peruta." They should not make any other comments, and should not say – even jokingly – that the ring is worth more than a "Shaveh Peruta." The groom must ensure that the ring or coin legally belongs to him before he gives it to the bride. When betrothing with a ring, it is customary to place the ring specifically on the forefinger, but if the groom mistakenly placed it on a different finger, the betrothal is nevertheless valid. A bride and groom should not perform a double ring ceremony. If the bride wishes to give her groom a ring, she should do so only after the Hupa ceremony.
