A widow who comes to collect her ketuba money form the orphans, must swear that the husband didn’t give her any of the ketuba money in his lifetime (just like all creditors need to do to collect from orphans on their father’s debts). The Rabbis were concerned she may swear falsely and therefore would not allow her to swear. Since they could no longer collect their ketuba money, Rabban Gamliel instituted that a woman could take a vow instead of swearing. Why is the concern only for widows? Why is a vow better than swearing in terms of concern for lying? Historically, Rav would not allow women to collect their ketubot because he saw that people didn’t take vows seriously. This lead to a woman getting very angry and caused the death of a Rabbi and as a result, Rav Yehuda make a public declaration endorsing Shmuel’s opinion against Rav. Why is there not a concern that a woman’s husband will cancel her vow or she will go to a chacham to annul the vow?