The three elements of eirusin (kiddushin), "Betrothal"
The formal statement of the law of eirusin (also called kiddushin), or "Betrothal", is found in the opening paragraph of the Mishnah treatise Kiddushin---
äÈàÄùÌÑÈä ðÄ÷ÀðÅéú áÌÀùÑÈìÉùÑ ãÌÀøÈëÄéí, åÀ÷åÉðÈä àÆú òÇöÀîÈäÌ áÌÄùÑÀúÌÅé ãÌÀøÈëÄéí: ðÄ÷ÀðÅéú áÌÀëÆñÆó, áÌÄùÑÀèÈø, åÌáÀáÄéàÈä... åÀ÷åÉðÈä àÆú òÇöÀîÈäÌ áÌÀâÅè, åÌáÀîÄéúÇú äÇáÌÈòÇì.
A woman is "acquired" [in marriage] through three things, and regains her independence through one of two things: she is "acquired" [in marriage] through kesef, and through sh'tar, and through biy'ah... and she regains her independence through a get ["deed" of divorce] or her husband's death.
- kesef (lit., "money") means that the bride-groom must give to the bride a coin, or anything of value, representing the "consideration" that the law of contracts requires for any contract to be legally binding. There was a difference of opinion in ancient times between the two rival authorities Hillel I and Shammai (ca. 40BCE) as to whether the value of the kesef "gift" should be nominal or substantial; the dispute was settled in favour of the former's opinion, that it need be only nominal as the woman is not being "bought" in any sense and so the contract "consideration" is purely symbolic. Originally the kesef "gift" could be any object, but eventually is became standardised as a wedding ring and this is now the universal practice among all Hebrews. The bride-groom places it on the forefinger of his bride's right hand and makes the formal declaration: äÂøÅé àÇúÌÀ îÀ÷ËãÌÆùÑÆú ìÄé áÌÀèÇáÌÇòÇú æåÉ ëÌÀãÇú îÉùÑÆä åÀéÄùÒÀøÈàÅì---"Behold: by this ring you are 'betrothed' to me, according to the law of Mosheh and of Yisrael."
- sh'tar (lit. "document") refers to signing the k'tubbah, or marriage "contract", which formalises the responsibilities to the bride that the bride-groom undertakes, and also details her rights in the event of her husband's death or the breakdown of the marriage.
- biy'ah is a Talmudic word for sexual intercourse. Unlike the first two elements of eirusin (kiddushin), which must be performed in public and witnessed by two Witnesses (who also sign the k'tubbah) as prescribed by torah law, this third element does not take place in public and is not "witnessed", for obvious reasons of decency. After the public formalities have been completed (i.e. giving her the ring and signing the k'tubbah), which are preceded by the usual Benediction for wine and a special kiddushin Benediction, the happy couple share the cup of wine used by the celebrant and are then taken to a private room where their first sexual intimacy takes place. There should be formal Witnesses to their entrance together into the private chamber. Once inside, in earlier times, it was usual for the bride-groom to make a second declaration similar to the one he made publicly when putting the ring onto the bride's finger, and for him to do so loudly enough for the Witnesses, standing outside the chamber, to be able to hear it; however this practice was considered indiscreet and was discontinued a long time ago.
Something that is not widely known is that before the eirusin (kiddushin) formalities begin, it is customary for the bride-groom to enter the bridal room, where the bride will often be seated on a kind of "throne", surrounded by her (female) relations and friends---and the bride-groom ceremonially lifts her veil to make sure that he is marrying the right girl (think about Ya'akov and Rahel if you're wondering why this custom began).