Talmud for Ketubot 1:1
בְּתוּלָה נִשֵּׂאת לַיּוֹם הָרְבִיעִי, וְאַלְמָנָה לַיּוֹם הַחֲמִישִׁי. שֶׁפַּעֲמַיִם בַּשַּׁבָּת בָּתֵּי דִינִין יוֹשְׁבִין בָּעֲיָרוֹת, בַּיּוֹם הַשֵּׁנִי וּבַיּוֹם הַחֲמִישִׁי, שֶׁאִם הָיָה לוֹ טַעֲנַת בְּתוּלִים, הָיָה מַשְׁכִּים לְבֵית דִּין:
A virgin is married on the fourth day [and not on the night preceding the fifth day, for we apprehend that he might then be preoccupied with the wedding and not be able to cohabit], and a widow on the fifth day. For the batei-din convene in the cities twice a week, on the second day and the fifth day, so that if he have a claim of (absence of) virginity, [such as: "I cohabited and did not find blood," whether she be a minor, a na'arah, or a bogereth, or: "I found an open door," if she were a minor or a na'arah (but not if she were a bogereth)], he can rise early to beth-din [when his anger is still upon him, lest he be assuaged and "cool off," and keep her; and it may be that she were adulterous under him (i.e., during the time of betrothal), in which instance she is forbidden to him. The gemara asks: Let him marry her on the first day, and if he has a claim of virginity, he can rise early to beth-din on the second day. And it answers: The sages were solicitous of the welfare of the daughters of Israel, that the groom occupy himself with the (wedding) feast three days: the first, second, and third day, and that on the fourth day he marry her. And when batei-din do not sit on the second and fourth days, a woman can be married on any day, provided that he occupy himself with the feast for three days. And out of solicitude for the poor, it is the custom in some places to marry on Sabbath eve. The reason that a widow is wed on the fifth day is that the sages were solicitous of the welfare of the daughters of Israel, so that (in this instance) he can rejoice with her three days — the fifth, the sixth, and the Sabbath. One who marries a widow is forbidden to work for three days and one who marries a virgin may not work all seven. As to birchath chathanim ("the blessings of the groom"), both a man being married for the first time, who weds a widow, and a widower who weds a virgin, bless birchath chathanim all seven days. And a widower who weds a widow blesses birchath chathanim one day.]