הסכמי קדם-נישואין

(4) If the husband takes an oath to give a bill of divorce, they need to make him renounce it beforehand, in order that it not look like he is being compelled. But if it was just a pledge he made, he can give it if he wants, because this is not similar to being compelled. Rem''a: and this is the ruling if he receives an acquisition to divorce. But if he accepts fines if he does not divorce, this is not called compulsion, since his bill of divorce was dependent on another thing and he will be able to give the fine and not divorce. And there are those that are stringent even in a case like that. And it's better to worry a priori and exempt him from the fine. But if he already divorced(her) because of this, and even did so from the strength of the oath he made to divorce, the bill of divorce is kosher, since, from the outset, they did not compel him by this. There are those that say that say that it is not called compulsion unless they compel the man himself, but if they compel someone else until his friend divorces, even a son for his father or vice versa, this is not called compulsion. There are those who are stringent in the case of a father and son. See later on in 152 for these laws.