In Jewish law, it is customary for the husband to execute before the nuptials an obligation in writing termed “Kethuba”. This obligation was termed Kethuba (the marriage deed). So far as the subsequent history of the Kethuba is concerned, Dr. Mielziner summarises it thus at pages 88-89: –
“From the time when the husband’s right of divorcing his wife against her will was restricted by the generally adopted decree of the Synod of R. Gershom (eleventh century), the Kethuba lost its former importance. Nevertheless, it was retained as an ancient custom, and looked upon as a kind of formal marriage settlement.
As the wife, in our days, is sufficiently protected by the civil laws of the country, and in many cases also by special marriage settlements made in a more legal form, the Kethuba is generally regarded as an unnecessary, useless formality, and is almost entirely dispensed with.”
In Lindo v. Belisario  I Haqq. 216 the Consistory Court of London, on the authority of the answers given by Beth Din in England to whom certain questions were submitted for their answers, held that the execution of a Kethuba was customary but was not essential to the validity of a Jewish marriage.
In Joshua v. Arakie  I.L.R. 40 Cal. 266, a Division Bench of the Calcutta High Court held that the Kethuba was a necessary but formal incident of the marriage contract and ceremonial in Calcutta between those of the Jewish faith and created no right in favour of a Jewish widow to recover the sum mentioned therein from her deceased husband’s estate.
In Rachel Benjamin v. Benjamin Solomon Benjamin, Crump, J., did not believe that the parties before him intended that the Kethuba executed by them should be acted upon and negatived the wife’s claim for recovery of the amount mentioned therein.
The real purpose of Kethuba
The declaration contained in the Kethuba that the husband takes the bride as his wife according to the law of Moses and Israel does not in any way carry the matter further and it still remains to be ascertained from that law what the legal nature of such a marriage is.
Similarly, the husband’s undertaking to honour, feed, clothe and look after his wife as Jews have done, does not also show that the obligations which a husband undertakes towards his wife in a Jewish marriage consists merely of such of them as he has expressly contracted to by the Kethuba.
The Kethuba’s real purpose seems to be what Dr. Mielziner has set out above, viz. a contractual protection for the wife entitling her to receive a particular sum of money in certain eventualities.
 Rev. Dr. M. Mielziner’s “The Jewish Law of Marriage and Divorce in Ancient and Modern Times”, second revised edition published in 1901