The History of the Ketubah
There is a debate in the Talmud as to whether the ketubah is of Biblical or Rabbinical law. If it is of biblical law, then the ketubah law is over three thousand four hundred years old. If it is of rabbinic law, it would be somewhat more recent, the exact year of the enactment is not known.
The primary reason for the requirment of the ketubah is stated in the Talmud, so that divorce would not be taken lightly. That is, to make the marriage more secure by setting in advance a substantial monetary settlement that would be paid to the wife upon the dissolution of the marriage. At the same time, this settlement also provided the divorcee with some money to live on after the divorce. A minimum was set at 50 shekalim which was enough to sustain a person for one year. Of course, the amount was ordinarly much higher where the husband was from a wealthy family.
The same lump sum amount would be paid to a widow from the deceased husband estate, however in the case of widowhood, the wife had the option to continue living in the house of the deceased, and be supported by the estate until she remarries.
The ketubah also stated other obligations, some of Biblical law as well, requiring the husband to provide food shelter and clothing, and medical care if needed.
The Text of the Ketubah
Many of the phrases that were incorporated in the original ketubah as stated in the Talmud no longer appear in the present day ketubah. This has been the case for many centuries. The present text common in all ashkenazic lands is taken from the authoritative work "Nachlas Shiva" written in the seventeenth century. (The text of present day sefardic ketubos, although a bit more wordy than Ashkenazic ones, are basically the same ) The omissions include the obligation to pay ransom in case the wife is kidnapped, and to pay for her funeral if she dies before the husband. These obligations need not be stated explicitly in the ketubah, because these are mandatory marriage obligation and its documentation is unnecessary.
The original purpose of the ketubah is no longer material, since the present halacha prohibits divorce without mutual consent except in rare circumstances. The monetary considerations are therefore negotiated between the two parties, and prior agreements are no longer needed. In our times, the most important phrase in today's Ketubah is the husband's written promise stating " I will work for you, honor you, and support and provide for all your needs, and live together with you as is the way of all Jewish husbands who work, honor, and support their wives with honesty"..