Kiddushin 44 - 50
“It is a mitzvah to listen to the words of the Sages.”
The question under discussion in the gemara is what is the source for the statement of Rava that “devarim sheblev einam devarim” — i.e., whatever is in one’s heart (i.e., not verbalized) doesn’t have the power to contradict that which he actually says.
The gemara attempts to provide a source for Rava from a mishna that deals with a get for divorce. It states that if a man refuses to divorce his wife despite her being forbidden to him, the Jewish court forces him to agree to give the get and say “I want to give the get”. (This is necessary because a get must be given by the husband willingly.) The gemara suggests this a proof for Rava, since we can assume in his heart he does not want to give the get, despite the words that the court force him to say that proclaim that he wants to give it. This would prove that whatever is in one’s heart (i.e., not verbalized) doesn’t have the power to contradict that which he actually says. However, the gemara rejects this from serving as a proof, since “it is a mitzvah to listen to the words of the Sages”, and perhaps that is why he is saying that he wants to give the get.
The Rambam (Laws of Divorce 2:20) elaborates as to what is actually taking place in the mind and soul of the man in this case, and he writes why this is different from someone pressured into doing something that the Torah does not require him to do, such as selling or giving away something that he owns.
He explains: “When someone’s evil inclination has taken a hold on him to avoid fulfilling a mitzvah, or to commit a sin, and he is beaten until he does what he is obligated to do or refrains from what he is forbidden to do, he is not considered as acting against his will. Rather, it is he who has coerced himself with an evil attitude to act against his true will. We therefore view the man who is forced to divorce his wife as one who truly wishes to be a part of the Jewish People, and truly desires to fulfill the mitzvot and to refrain from transgressions, but who is the helpless victim of his evil inclination. Once he has been pressured to the point where his evil inclination is subdued and he declares his consent, we consider it as his having divorced of his own free will.”
- Kiddushin 50a