A man who makes a vow to Hashem... (30:3)
The Shulchan Aruch (YD 203:4) rules that one should be careful not to make a vow, even with regard to the fulfillment of mitzvos, such as giving tzedakah. However, two halachos later, the Shulchan Aruch seems to openly contradict this ruling when he writes that if one accepted upon himself to study a section of Torah and is afraid that he may be negligent, he may make a vow to learn that particular subject in order to urge himself to complete it.
The Taz (ibid. 5) reconciles these two rulings by differentiating between giving tzedakah and learning Torah. He explains that the yetzer hara is stronger when it comes to giving away money than when it comes to ‘simply’ fulfilling a mitzvah with one’s body with no monetary obligation. Therefore, one should not make a vow to give tzedakah since the yetzer hara is very strong in this scenario, and one may come to transgress his vow. However, regarding the vow to learn Torah, the yetzer hara is not as strong, and there is much less of a concern that the person will transgress their vow. Therefore, he may make a vow to learn Torah.
Some of the commentaries ask on the Taz’s explanation from the Gemara (Brachos 32b) that says that fasting is greater than giving tzedakah since fasting is done with one’s body, and giving tzedakah is done with one’s money. Seemingly, it is harder to do a mitzvah with one’s body as opposed to with one’s money.
Therefore, the commentaries explain the contradiction in the Shulchan Aruch as follows. The Gemara (Ta’anis 8b) says that when the Jewish people merely accepted on themselves to fast to nullify a certain decree, the decree was nullified. From here we learn that when one accepts to do a mitzvah, it is considered as though he did it already. (Obviously, on condition that he actually ends up doing it. However, the merit is already attributed to him from when he accepts the mitzvah upon himself.)
This is where Torah is different from all other mitzvos. The Gemara (Sota 21a) says that the merit of a mitzvah does not save one from the yetzer hara, whereas the merit of Torah study does save one from the yetzer hara. Therefore, when one makes a vow to give tzedakah, even though he may have the merit of the mitzvah, that still does not save him from the yetzer hara. This is why we are concerned that he may still not end up fulfilling his vow. However, when one vows to study Torah, and the merit of Torah study is already attributed to him, that merit will protect him from the yetzer hara’s influence, and he will end up fulfilling his vow.
To answer the commentaries’ question on the Taz, the Zera Shimshon says that the Gemara regarding fasting is not a good proof. This is because in Baba Kama (92a), we learn that a person is more comfortable losing money than having his body pained. That is why fasting is greater than giving tzedakah. It is not a proof that any mitzvah that is done with one’s body is harder; it is only a proof to a case where there is bodily pain involved that one would rather give up money than be pained.
But in the case where one made a vow to learn, there is no pain involved. In fact, when one learns Torah, they derive enjoyment! This is why we are not concerned that he will not fulfill his vow. On the other hand, when one vows to give tzedakah, we are concerned that he may justify not fulfilling his vow by saying that he doesn’t know if the person he wants to give tzedakah to is indeed worthy of receiving tzedakah. Perhaps he is a charlatan or the like, and because of this, the one who made a vow will refrain from fulfilling his vow.
