The ketubah is a unilateral agreement drawn by witnesses in accordance with Jewish civil law, in which they testify that the husband guarantees to his wife that he will meet certain minimum human and financial conditions of marriage, "as Jewish husbands are wont to do."
The Ketubah is the marriage contract that outlines the obligations of the husband to his wife, as well as the financial compensation due to the wife in the event of the marriage’s dissolution through divorce or widowhood. Similar to a Get (divorce document), the Ketubah is traditionally written in Aramaic, the common language of the Jews during Talmudic times.
The Sages extrapolated from the words of the Scriptures1 that all matters pertaining to the transacting of marriage and divorce must be effected in the presence of two witnesses. These witnesses will be able to testify regarding the marital status of the couple, if doubt in this area ever arises; but more importantly, they actually effect the marriage (or divorce). According to Jewish law, the two witnesses play the most pivotal role in the marriage ceremony.