The first Mishna in Massekhet Ketubot teaches that there were specific days for marriages during that period in history. Women who were virgins getting married for the first time would get married on Wednesdays, while widows would get married on Thursdays. The Mishna does not offer any reason for establishing wedding dates on Thursdays for widows, but explains that the establishment of Wednesday for first-time weddings stems from the desire of the Sages to encourage the husband to come to beit din on Thursday morning should he find that his wife was not, in fact, a virgin. Since Jewish courts ordinarily sat on Mondays and Thursdays, it made sense for weddings to take place on Wednesdays.
The Gemara goes on to explain that the establishment of Thursdays for widows – and, for that matter, the reason that first-time weddings did not take place on Sundays – was because of shakdu: that the Sages wanted to ensure at least three days of preparations for the wedding. In effect this meant that weddings could take place only at the end of the week.
It should be noted that the Mishna’s concern with the possibility that the woman was not a virgin was only a problem in Talmudic times when there was a significant amount of time between the betrothal (kiddushin) and completion of the marriage (nissu’in). In such a situation, if the woman had committed adultery during that period, she would be forbidden to her husband, and it would be essential for him to present the facts to the courts to rule on what happened. Today, when the kiddushin and nissu’in take place one after another under the ḥuppah, this concern no longer exists. In any case, the basic halakha of the Mishna was one that raised a series of questions among the rishonim. Do we truly need to be suspicious of an adulterous act? And even if we do suspect that the woman had a sexual relationship with someone other than her husband, perhaps it took place before the kiddushin, and she will be permitted to her husband in any case. In short, why is there a need to establish such a rule for a most unlikely case?
Many explanations are given in answer to these questions. Rashi suggests that we are simply trying to bring a suspicious case to beit din in the hope that witnesses will step forward to help us clarify the matter. The Shiṭṭa Meḳubbeẓet suggests that the Mishna offers only one reason for the rule. The main reasons are those mentioned in the Gemara – shakdu, as well as the idea that there is a special blessing for marriage on Thursday (i.e. Wednesday night, after the wedding) and Friday, paralleling the blessings given on the fifth and sixth days of creation (see Bereshit 1:22, 28).