Why Moses had to annul his vow with in the presence of Yitro TB Nedarim 65

On today’s daf TB Nedarim 65 the Gemara learns a new halakha based on yesterday’s story concerning Moses and his vow to his father-in-law Yitro.

“It is taught in a baraita (Tosefta 2:12): With regard to one prohibited by a vow from deriving benefit from another, they dissolve the vow for him only in the presence of the one who is the subject of the vow. The Gemara asks: From where are these matters derived? Rav Naḥman said: As it is written: “And the Lord said to Moses in Midian: Go, return to Egypt; for all the men are dead” (Exodus 4:19). Rav Naḥman notes that the verse specifies where God spoke to Moses, and explains that God said to him: In Midian you vowed to Yitro that you would not return to Egypt, go and dissolve your vow in Midian. And where does it say that Moses vowed to Yitro? For it is written: “And Moses was content [vayo’el] to dwell with the man” (Exodus 2:21). The word vayo’el is related to the word ala, and ala means nothing other than an oath, as it is written: “And he…brought him under an oath [ala]” (Ezekiel 17:13), and the halakhot of dissolution of oaths are identical to those of dissolution of vows.”

The Ron ד"ה תַּנְיָא: הַמּוּדָּר הֲנָאָה מֵחֲבֵירוֹ אֵין מַתִּירִין לוֹ אֶלָּא בְּפָנָיו cites Yerushalmi’s two reasons why the vow has to be dissolved before the one who was the subject of the vow. The first reason is embarrassment (בּוּשָה). If the vow benefits the other person, the rabbis didn’t want the person who made the vow to rush and annul it. If he is embarrassed by dissolving the vow, he might think twice before doing so. The second reason is suspicion (חָשׁוּד). If he annuls his vow without the other party knowing, people will suspect him of violating his vow without knowing the circumstances. By having both parties together, news will spread that the vow has been dissolved. The Ron qualifies the difference between the two reasons. If the reason is embarrassment, then the two parties always have to be together when the vow is dissolved. If the reason is suspicion and the annulment is announced, then the two parties don’t have to be together when the vow is dissolved.

Moses’ vow certainly benefited Yitro. He vowed that he would not leave Midian with his new wife. Even though God gave him the petakh to annul his vow, Moses had to do so in front of his father-in-law. I think both reasons can work in tandem to explain why God insisted Moses dissolve his vow in front of Yitro.

When the vow benefits the subject of the vow, some commentators explain that the phrase “in his presence (בְּפָנָיו)” means that the subject of the vow must also agree to the annulment. Otherwise the vow still remains in force. See the Rosh. Obviously, Yitro must have given his consent as well.