In order to answer the question above, it is important to point out another difficulty with Rambam’s formulation of the marriage laws.
In the process of Jewish marriage there are two steps: (a) Betrothal (Eirusin), an acquisition through either money, a contract, or marital relations, and (b) Actual Marriage (Nissuin), which is brought about through a chuppah.
Although through Betrothal (Eirusin) alone the woman is considered to be a “married woman,” nevertheless, there are various facets in which the marriage is only completed through Nissuin. Then the woman is considered married in all respects.
Consequently, according to the idea that Nissuin is the culmination of Eirusin (Betrothal), the manner in which Rambam transcribes the laws is troublesome. Rambam, in the beginning of his Laws of Marriage, only explains the concept of Betrothal (Eirusin) and does not explain the concept of actual marriage (Nissuin) until Chapter 10. There he writes:
Text 9
Even when [the husband] consecrated [his arusah] by having sexual relations with her, he is forbidden to engage in sexual relations with her again until he brings her to his home, enters into privacy with her, and thus singles her out as his [wife]. [Their entry into] privacy is referred to as entry into the chuppah, and it is universally referred to as Nissuin.
Rambam, Laws of Marriage 10:1
Why did Rambam wait until chapter 10 of his Laws of Marriage to explain the concept of Nissuin, when Nissuin is the completion of the entire marriage process? Betrothal is only a step in the marriage process, whose goal is to ultimately reach the stage of Nissuin. Rambam should have instead explained this stage of the marriage in Chapter 1, together with his explanation of Betrothal (Kiddushin), as it is of utmost importance.
Not only is Nissuin an important step in marriage, but the whole Kiddushin (Betrothal) is for the purpose of Nissuin. If so, it is all the more surprising that Rambam only mentions the concept of Nissuin in Chapter 10 of his Laws of Marriage and not at an earlier point.
Kiddushin and the Giving of the Torah
Rambam’s view of marriage can be understood as such that the main novelty of the Torah concerning marriage is in regard to the classification of Kiddushin—an innovative concept which was created through the Torah commandment. However, concerning the idea of Nissuin, even after the giving of the Torah, the concept was did not undergo any change.
The concept of Nissuin is the reality of actual married life, as Rambam writes, that Betrothal lasts “until he brings her to his home... as his [wife].” Within this idea, there is no dramatic shift from before the giving of the Torah to after the Torah was given, and the concept of Nissuin is still the idea of a spousal relationship.
This explains why Rambam begins with stating the historical background of marriage, that “Once the Torah was given, the Jews were commanded that when a man desires to marry a woman, he must acquire her as a wife ... [Only] after this, does she become his wife,” and goes on to explain the process of Kiddushin, though not the concept of “marriage,” Nissuin.
The reason for this is because concerning the idea of “becoming his wife,” this phenomenon remained as it was before the Torah was given. The only thing that Torah changed was the idea that “he must acquire her as a wife.”
It is for this purpose too, that Rambam prefaces an account of the marriage proceedings prior to the giving of the Torah. This is not only a preface to understand the Torah’s innovative concept of Kiddushin, but it also serves as an explanation for the concept of marriage (Nissuin) as it now exists after the giving of the Torah.
Accordingly it is understood, that not only does Rambam not leave out the concept of Nissuin, but on the contrary, this is the first thing that he explains in his Laws of Marriage. Only after he explains the main part of marriage—Nissuin—does he begin explaining the concept of Kiddushin. Rambam’s explanation of marriage before the giving of the Torah is not historical in nature but should rather be viewed as an elucidation for the concept of Nissuin as it is today.
Now as well, can the question that was posed earlier, as to why, concerning marriage, Rambam explains the manner that it was done prior to the giving of the Torah, while concerning divorce he does not, be answered.
The concept of marriage itself (Nissuin) remained the same before the giving of the Torah and afterwards. It is therefore apropos to explain the concept of marriage as it was prior to the giving of the Torah, as there is relevance now as well. However, the concept of divorce and leaving the marriage as it was before the giving of the Torah is completely obsolete today (for a Jew), and therefore there is no purpose of explaining it. Therefore, although Rambam found it necessary to explain the idea of marriage as it was before the giving of the Torah, he found it superfluous to explain the concept of divorce, as it was before the giving of the Torah.
