The kethuba begins with the day of the week on which the marriage takes place. It also begins with the letter beth . In Made in Heaven: A Jewish Wedding Guide, (Moznaim Publishing, 1983) Rabbi Aryeh Kaplan (p. 107) points out that the first letter of each kethuba is the same as the first letter of the Torah. Just as the Torah attest to the bond between G-d and His people, the kethubah documents the bond between husband and wife. I would add to that what our Sages say about the beginning of the Torah fits in well with that observation. The Torah begins with the same letter that begins the word bracha [blessing]. As the second letter of the alphabet, the letter beth also stands for two. It is necessary to expand beyond the singular in order to come to a state of blessing. (The Maharal explains that the association is not arbitrary but inherent in the meaning of blessing,) The concept is most apt for a marriage in which two people come together in an event of blessing, highlighted by the sheva brachos [seven blessings].