The custom among Sepharadim – based upon the ruling of the Shulhan Aruch (Eben Ha’ezer 1:11; listen to audio recording for precise citation) – is that the groom takes a formal oath at the time of the signing of the Ketuba document at the wedding. In this document, the groom commits himself to various monetary and personal obligations toward the bride, each community according to its particular customs. Although we generally avoid oaths, the Shulhan Aruch writes that it is proper for a groom to verbally swear to fulfill the commitments written in the Ketuba, due to the unique severity and importance of this commitment. Hacham Ovadia Yosef ruled that one should follow this custom, which, according to some, dates back to the time of the Rambam (Rabbi Moshe Maimonides, Spain-Egypt, 1135-1204).
If, for whatever reason, the groom is not making an oath, then the line in the text of the Ketuba that mentions the oath must be erased. Quite obviously, the witnesses cannot sign on a document which affirms that the groom swore to uphold the marriage obligations if he did not actually take such an oath. Therefore, if the groom is not taking an oath, this sentence must be omitted from the text of the document.
In any event, as mentioned, it is proper for the groom to take this oath, in accordance with time-honored tradition.
In addition to signing the document, the groom must also perform a "Kinyan" – a formal act expressing his acceptance of the commitments. In order for a legal commitment to be Halachically binding, it must be accompanied by a formal act of "Kinyan," and therefore the groom must perform an act to affirm his commitments. This is done through the lifting of a Sudar (handkerchief). The officiating Rabbi places a handkerchief on the table, and the groom takes it. This "Kinyan" is a "Kinyan Halipin" – a formal exchange, whereby the groom takes the handkerchief and in exchange, he transfers to the Rabbi, who is representing the bride (it is considered improper for the bride to represent herself in a monetary matter), the rights he commits to his bride.
The witnesses selected to sign the Ketuba must see the act of "Kinyan," meaning, the groom’s lifting the handkerchief. After all, they are signing a document affirming that the groom made a "Kinyan," and they obviously cannot testify to this effect if they did not actually see the "Kinyan." Very often there is a lot of commotion at the signing of the Ketuba, as the photographers and relatives are crowding around, and it could easily happen that the witnesses’ view is obstructed. The witnesses must ensure to see the groom lift the handkerchief, which constitutes the "Kinyan" act to which they testify by signing the document.
However, some Halachic authorities maintain that if the witnesses signed the Ketuba without seeing the "Kinyan" act, the document is nevertheless valid. For one thing, it can reasonably be assumed that since the ceremony was conducted under the auspices of competent Rabbis, it was done properly and in accordance with Halacha, and included a "Kinyan" act. Therefore, even if the witnesses did not actually see the "Kinyan," they can nevertheless sign since they were present and saw the Rabbi and the groom preparing the Ketuba. Secondly, since the groom instructed the witnesses to sign the document in which he declares his commitment to the obligations written therein, this suffices to allow the witnesses to testify to the "Kinyan." There is a Halachic principle called "Hoda’at Ba’al Din Ke’me’a Edim Dameh," which means that a person’s confession that he owes money bears as much legal force as the testimony of one hundred witnesses. Thus, if the groom tells two witnesses that they may sign a document in which he commits himself to certain obligations, this itself is proof to the commitment. This is similar to the case of a person who announces to two witnesses that he owes somebody $1,000. That second party can then take that person to court on the basis of his testimony and demand the money, even if there really was no $1,000 debt. Similarly, regardless of whether the witnesses saw the "Kinyan," a groom can tell them to sign on the document affirming that he made such a commitment.
It must be emphasized, however, that this applies only "Be’di’abad" – after the fact. As mentioned, the witnesses should ensure to see the "Kinyan," though if they realized after signing that they did not see it, the document is nevertheless valid.
Summary: Sephardic custom is for the groom to make an oath at the time of the signing of the Ketuba committing himself to the obligations mentioned in the Ketuba. The witnesses who sign the Ketuba must ensure to see the act of "Kinyan" – the groom lifting the Rabbi’s handkerchief whereby he commits himself to the obligations mentioned in the Ketuba. If the witnesses realized after they signed that they had not seen the "Kinyan" act, the Ketuba is nevertheless valid.
