Jewish marriage law consists not only of ishut, the determination of prohibited and permitted partners, but of kiddushin, the legal process of establishing the marriage bond. The Bible has no single word for marriage, as it has none for religion. But the codes define it by these two categories: ishut and kiddushin, persons and process.

Maimonides begins his code on marriage with the Torah's unconditional requirement that a man and a woman may live together only with the formal sanction of kiddushin.

Before the revelation (at Sinai), a man would meet a woman on the street and if both desired marriage, he would bring her into his home and have intercourse privately [without the testimony of witnesses] and she would become his wife. When the Torah was given, the Jews were instructed that in order to marry a woman, the man should "acquire her" in the presence of witnesses and then she would become his wife. As the Torah says, "when a man takes a woman and has intercourse with her." This taking is a positive commandment and is performed in one of three ways—with money, by contract, or by cohabitiation... and it is everywhere called kiddushin or erusin. And a woman who is "acquired" in one of these three ways is called mc'kudeshet or arusah [a betrothed woman]. And as soon as she is "acquired" and becomes betrothed, even though she has not cohabited and did not even enter the groom's home, she is a married woman. Anyone, other than her husband, who cohabits with her, is guilty of capital punishment. If he wishes to separate from her, he requires a divorce.

Maimonides tells us that a Jewish marriage consists of two stages. The first is betrothal, kiddushin. The second is the nuptials, chuppah.

Kiddushin (a rabbinic term) is accomplished by kichah (a biblical term), the "taking" of a woman by a man, in one of three ways (in ages past):

1. Money (kessef). The man gives the woman money, even a low denomination coin, or the equivalent of money—today a ring is customary—before two witnesses and says, "You are hereby betrothed unto me with this ring in accordance with the laws of Moses and Israel." The bride, by her acceptance, indicates her willingness to be married to the groom.

2. Contract (she'tar). The man gives the woman a deed, before two witnesses, which contains the names of the couple and the groom's marriage formula. This deed is not in the nature of evidence of the marriage, but is for the purpose of effecting the bond of marriage. It is not to be confused with the ketubah, which is given as protection of the woman after the kiddushin.

3. Intercourse (bi'ah). After the man has addressed the marriage formula to the woman before two witnesses, the couple retires to a private place with the intent of effecting the betrothal through intercourse. The Sages considered this to be gross, virtually an act of prostitution, and in the third century Rav decreed flogging for those who chose this manner of betrothal. Nonetheless, if the marriage was performed in this way it was legally valid.

Only kessef is performed today; both intercourse and contract as forms of betrothal are obsolete.

Kichah ("taking," the formal acquisition) approximates the economic term kinyan and seals the marriage. Because this is the first stage in the process of creating a covenant of partnership, unions that are prohibited and void, such as incest, are never referred to in the Torah by the term kichah, but as she'khivah (sleeping together). In regard to almost all valid marriages, even those that are prohibited, the Torah makes specific reference to kichah.

This first stage of marriage is not a preliminary agreement to contract a marriage at a future date (like the western concept of engagement), but an integral component of the two-step marriage process. The betrothal portion is a sort of inchoate marriage; from that point onward, the couple is considered married. Until the second step is taken, however, the bride may not cohabit with the groom (or any other man). In this social suspension that marks the difficult transition from the single life to the married state, the couple is together yet apart. Until the twelfth century, this first stage of marriage lasted up to one year in order to make preparations for the final step. The second stage of the marriage process is the consummation. It is alternatively termed nissuin, meaning elevation of status, from nassa, coming by carriage from the father's home to the groom's; or chuppah, wedding canopy.

The Bible begins to use the term kichah as a preliminary to marital intercourse only after the Torah is received at Sinai. From this time forward, all Jewish marriages must have both components in order to be valid. The Rabbis, in order to make this perfectly clear to the couple, framed the betrothal blessing to read: "...who has forbidden us the betrothed [arusot], and permitted us those who are married to us by chuppah and kiddushin."

By the twelfth century in Germany and France, the two elements were no longer separate but were fused into one ceremony and that is how marriage is performed to this day. The wedding ceremony begins with the betrothal, which consists of the blessings; the kinyan (the formal acquisition by means of the giving of the ring); and the recitation of the marriage formula. This is followed by a reading of the ketubah (the marriage contract). The marriage is finalized by the chuppah ceremony, which consists of the seven blessings, and yichud, when the bride and groom are brought together in a private room to symbolize the consummation of the marriage.

The reasons for combining the two ceremonies offer interesting insights into the moral concern of the Rabbis, the history of the period, and the economic plight of the Jews of the Middle Ages. Rashi, the classic commentator, offers the simple explanation that the costs were too burdensome. The families would be shamed if they could not afford a sumptuous all-day banquet in honor of the betrothal, and still another banquet in celebration of the nuptials. Putting the ceremonies together eliminated the need for two banquets. This also helps to explain the ancient custom of holding the betrothal on Friday afternoon. The Shabbat dinner of Friday night doubled as the betrothal celebration, and the nuptials were held on Saturday night after sundown.

Conditions for medieval Jews were unstable and hazardous. During the year between the betrothal and the nuptials, families might be compelled to flee to distant shores. That would leave the betrothed woman an agunah, (literally, a chained woman) married yet not married, and unable to live with her fiancé and not permitted to marry anyone else without a divorce, which, considering the distance and lack of communications, was often quite difficult to arrange. Holding the two ceremonies in quick succession offered a practical solution to this distressing situation.

Morally, the fusion of the two ceremonies accomplished the removal of temptation from the betrothed couple, who were not permitted to cohabit during the year of betrothal. Indeed, we have seen that the betrothal blessing in Talmudic days is worded precisely to prevent that eventuality. In the era when the idea of romantic love spread wildly throughout Europe, the temptations must have been great to relinquish the ideal of chastity in the expectation of the forthcoming marriage. This problem was not confined to the romantic era. In the third century, preventing these intimacies became a widespread problem in Judea, where poor grooms were housed by wealthier in-laws in the home of the prospective bride. The law took recognition of this problem when it refused to allow the complaint from a groom on the day after the chuppah that the bride deceived him because she was not a virgin. Because he and the bride lived in the same house, the groom could not be presumed innocent; in fact, it raised the possibility that it was he who deflowered the bride. In the very first chapter of the Talmudic tractate of Ketubbot we read: "If in Judea a man boarded with his father-in-law but had no witnesses, he can not institute virginity proceedings against her, because he had already been alone with her."