Three interesting customs seen at traditional Jewish weddings are based on a problem raised by Tosefot in our gemara and the resolution provided by Rabbeinu Tam.

A man performed kiddushin (made a woman his wife) by giving her some expensive garments which he said were worth fifty zuzim. In the end it turned out that the garments were actually worth that sum but no one had made an assessment of their value before the woman accepted them and consented to the marriage. The Sage Rabbah held that such a kiddushin is valid; Rabbi Yosef contended that, since no assessment had been made, the woman was not really certain that she was receiving the promised value and therefore did not really give her consent to marriage.

After a long series of proofs offered for each of these views, the gemara concludes with a ruling that an assessment of such garments is not necessary. Tosefot asks why the gemara did not simply state that we rule like Rabbah, who rules out the need for assessment, just as it does in the very same sentence in regard to ruling like the sages Rabbi Elazar and Rava, mentioning their names rather than their subject. Rabbeinu Tam, one of the leading Tosefists, deduces from this deviation that the gemara rules like Rabbah only in cases such as expensive garments, because their value is more of less generally known and it is unlikely that the woman would have assumed she was not receiving the value promised. If the object given to her, however, is a gem whose value can vary greatly, then there must be an assessment made before the woman accepts kiddushin because she is likely to assume a value much greater than what the gem is worth and she does not consent to a lesser value.

Tosefot concludes that this is the reason for the custom that the ring given for kiddushin not contain a gem; it is so that there will be no danger of the woman speculating about its undetermined value.

Two more customs related to this are mentioned by Rema (Shulchan Aruch Even Haezer 31:2). One is that the bride wears a veil over her face so that she will not stare at the ring offered her and speculate about its value. Another is that the rabbi in charge of the wedding ceremony (the mesader kiddushin) shows the ring to the two witnesses and loudly asks them if they can see that it is worth a pruta, the minimal value necessary for effecting kiddushin. This is intended to convey to the bride that she is prepared to consent to kiddushin even if it is only worth that much and thus eliminate the danger of speculation which might raise problems in regard to her consent.

Kiddushin 9a

Whoever is not expert in the laws of divorce and marriage, said Rabbi Yehuda in the name of the Sage Shmuel, should not be involved in them.

Why, asks Maharsha, does this sage mention divorce before marriage when the chronological order of these two is the reverse?

One answer is based on Rambam’s explanation for Mesechta Kiddushin following Mesechta Gittin in the order of the Talmud. Since the Torah uses the expression "she will go out from his home and become the wife of another" (Devarim 24:2), this pattern of placing divorce before marriage was followed in regard to the order of the Talmudic tractates.

Maharsha, however, offers another answer with serious practical implications. The laws of kiddushin are rather well known and the ramifications of a single woman being made permissible to a man are relatively not so serious. This is why it is customary to authorize rabbis who are familiar with the laws of kiddushin to perform marriage ceremonies. When it comes to the laws of gittin, however, there are so many intricate laws involved in the writing and delivery of a valid divorce document. The ramifications of ignorance here are also far more serious because the result may be to permit the remarriage of a woman who is still legally married. For these reasons, only rabbis who are expert in the laws of gittin are empowered to deal with divorce matters.

In order to stress the greater caution required in regard to divorce, the aforementioned statement placed the laws of gittin before the laws of kiddushin.

Kiddushin 13a