Nedarim 90 - How to revoke an non-existent vow
Normally, a husband can annul has wife's vow if it afflicts him or her. Suppose, however, she makes the following vow: she will be prohibited to derive any benefit from her husband if she ever does any service to his father. This vow does not yet exist. Nevertheless, it can be annulled, for the following reasons: it does involve self-affliction, and it is bound to happen.
There was a man who prohibited all benefit from the world on himself if he marries without first learning the laws of proper behavior. In the end, he was unable to learn, but due to his vow, he could not get married. Rav Acha tricked him into marrying, by telling him that the vow was invalid. Then, after the vow did become valid, he pushed him into dirt - so that he needed a cleaning service, something that his vow prohibited.
Now, in this state, he Rav Acha brought the man to Rav Chisda, who was a Sage empowered to annul vows. Who can be as wise as Rav Acha, to act like this? Why did Rav Acha have to go this? - Because he did not agree with the ruling above that a vow that is inevitable can be annulled before it happens. Rather, according to him, the vow had to exist before anything could be done about it.
Art: Double Portrait of a Husband and Wife with Tulip Michiel Jansz. van Mierevelt